Background: Prior research suggests naturalistic single-trial appetitive conditioning may be a potent phenomenon in humans, capable of modulating both motivation and attention. In this study, we aimed to characterise the neural correlates of this phenomenon using functional Magnetic Resonance Imaging (fMRI) paradigms Methods: Twenty-three healthy adults (12 males) underwent conditioning during which they ate a novel 3D object made from white chocolate (CS+) and handled a similar object made from plastic (CS-). Brain activity was recorded before and after conditioning during a passive viewing paradigm Results: A naturalistic CS+ was rated as more highly craved, better-liked and elicited greater expectancies for chocolate than the CS- after conditioning. An exploration of the interaction between time (pre- and postconditioning) and CS type (CS+, CS-) during the passive viewing task suggested enhanced activation from pre- to post-conditioning in the right superior frontal gyrus (R.SFG) in response to the CS-. Conclusion: Results reveal neural correlates of single-trial appetitive conditioning and highlight a possible role of response inhibition during learning about non-rewards, perhaps optimizing motivated behaviour. These findings contribute to our understanding of the neural mechanisms underpinning rapid reward and non-reward learning, and may inform development of behavioural interventions for reward-driven overeating.

Background: The reward value of palatable foods is often cited as an important influence on eating behaviors, including intake of sugars. However, human neuroimaging studies have generated conflicting evidence on the basic neural representation of taste and reward responses to caloric sweeteners (sucrose and glucose), and most relevant studies have used small subject numbers. Objective: We conducted a systematic review and a coordinate-based meta-analysis of studies reporting brain responses to oral sugar solutions. Methods: A systematic search of MEDLINE, Scopus, and PsycINFO through October 2019 identified fMRI studies (in healthy human adults, including those with overweight or obesity) assessing differences in responses to purified sweet and nonsweet taste stimuli. Data were extracted with the primary objective of quantifying evidence for the activation of brain regions associated with caloric sweet taste sensation. We used activation likelihood estimation meta-analysis methods. We also performed multiple sensitivity analyses to assess the generality of effects. Results: Of 455 unique articles, 15 met the criteria for inclusion. These contributed to 2 primary meta-analyses: 1) sucrose (13 experiments, 179 coordinates, n = 241) and 2) sucrose + glucose (16 experiments, 209 coordinates, n = 262). Consistent activation was apparent in primary taste areas: insula (69.2% of studies) and opercular cortex (76.9% of studies), precentral gyri (53.9% of studies), and globus pallidus and postcentral gyrus (30.8% of studies for each). Evidence of reward activity (caudate) was seen in the primary analyses (30.8% of studies) but not in sensitivity analysis. Conclusions: We confirm the importance of primary taste areas for gustatory processing in human adults. We also provide tentative evidence for reward-related caudate activity in relation to the sweet taste of caloric sugars. A number of factors affect the observation and interpretation of brain responses, including reward-related activity. Firm conclusions require confirmation with large data set studies.

BACKGROUND:Cannabis intoxication is commonly reported to increase appetite and enhance appreciation of food (the 'munchies'). These effects are attributed to activation of the endocannabinoid system. However, the psychological changes that underlie these phenomena are under-researched. We report here the results of an extensive online survey of cannabis users with an exploratory Cannabinoid Eating Experience Questionnaire (CEEQ).METHOD:Frequent cannabis users completed a 46-item questionnaire about their eating behaviour under the influence of cannabis. An English-speaking sample (n=591) provided data for the initial exploratory validation of the scale. A second Dutch-language survey (n=163) was used for confirmatory factor analysis. Test-retest reliability was based on a third English-speaking sample (n=40) who completed the revised, 28-item CEEQ twice across 2 weeks.RESULTS:Principal components analysis provided a two-factor solution. Factor 1 (hedonic) comprised 14 items that related primarily to the enjoyment and altered sensory aspects of eating. Factor 2 (appetitive) comprised a further 14 items related to motivational factors that instigate or promote eating. The two-factor structure was supported by confirmatory factor analysis. Both the hedonic and appetitive subscales had good internal reliability (α=0.92 for each subscale, in two independent samples). Good test-retest reliability was obtained for the revised 28-item questionnaire (ps<.01 for Total CEEQ and each subscale).CONCLUSION:The Cannabinoid Eating Experience Questionnaire provided a valid, reliable assessment of the psychological features of cannabis-induced alterations to appetite. Our data confirm that cannabis principally influences the motivational factors that lead to the initiation of eating and the hedonic factors implicated in maintaining eating.

Perceptually, itch is clearly discernible from pain, yet both sensations exhibit a substantial anatomical overlap with common peripheral transmission and recruited brain regions. For example, recent functional magnetic resonance imaging (fMRI) studies have observed activations in the pain-processing network during cowhage- or histamine-induced itch in the thalamus (Leknes et al., 2007Leknes S.G. Bantick S. Willis C.M. Wilkinson J.D. Wise R.G. Tracey I. Itch and motivation to scratch: an investigation of the central and peripheral correlates of allergen- and histamine-induced itch in humans.J Neurophysiol. 2007; 97: 415-422Crossref PubMed Scopus (123) Google Scholar, Mochizuki et al., 2009Mochizuki H. Inui K. Tanabe H.C. Akiyama L.F. Otsuru N. Yamashiro K. et al.Time course of activity in itch-related brain regions: a combined MEG–fMRI study.J Neurophysiol. 2009; 102: 2657-2666Crossref PubMed Scopus (63) Google Scholar, Papoiu et al., 2012Papoiu A.D. Coghill R.C. Kraft R.A. Wang H. Yosipovitch G. A tale of two itches. Common features and notable differences in brain activation evoked by cowhage and histamine induced itch.Neuroimage. 2012; 59: 3611-3623Crossref PubMed Scopus (130) Google Scholar, Valet et al., 2008Valet M. Pfab F. Sprenger T. Wöller A. Zimmer C. Behrendt H. et al.Cerebral processing of histamine-induced itch using short-term alternating temperature modulation–an FMRI study.J Invest Dermatol. 2008; 128: 426-433Abstract Full Text Full Text PDF PubMed Scopus (82) Google Scholar), insular cortex (Herde et al., 2007Herde L. Forster C. Strupf M. Handwerker H.O. Itch induced by a novel method leads to limbic deactivations a functional MRI study.J Neurophysiol. 2007; 98: 2347-2356Crossref PubMed Scopus (82) Google Scholar, Leknes et al., 2007Leknes S.G. Bantick S. Willis C.M. Wilkinson J.D. Wise R.G. Tracey I. Itch and motivation to scratch: an investigation of the central and peripheral correlates of allergen- and histamine-induced itch in humans.J Neurophysiol. 2007; 97: 415-422Crossref PubMed Scopus (123) Google Scholar), cingulate cortex (Mochizuki et al., 2007Mochizuki H. Sadato N. Saito D.N. Toyoda H. Tashiro M. Okamura N. et al.Neural correlates of perceptual difference between itching and pain: a human fMRI study.Neuroimage. 2007; 36: 706-717Crossref PubMed Scopus (94) Google Scholar), prefrontal cortex (Mochizuki et al., 2009Mochizuki H. Inui K. Tanabe H.C. Akiyama L.F. Otsuru N. Yamashiro K. et al.Time course of activity in itch-related brain regions: a combined MEG–fMRI study.J Neurophysiol. 2009; 102: 2657-2666Crossref PubMed Scopus (63) Google Scholar), postcentral gyrus (Herde et al., 2007Herde L. Forster C. Strupf M. Handwerker H.O. Itch induced by a novel method leads to limbic deactivations a functional MRI study.J Neurophysiol. 2007; 98: 2347-2356Crossref PubMed Scopus (82) Google Scholar, Ishiuji et al., 2009Ishiuji Y. Coghill R.C. Patel T.S. Oshiro Y. Kraft R.A. Yosipovitch G. Distinct patterns of brain activity evoked by histamine-induced itch reveal an association with itch intensity and disease severity in atopic dermatitis.Br J Dermatol. 2009; 161: 1072-1080Crossref PubMed Scopus (120) Google Scholar, Papoiu et al., 2012Papoiu A.D. Coghill R.C. Kraft R.A. Wang H. Yosipovitch G. A tale of two itches. Common features and notable differences in brain activation evoked by cowhage and histamine induced itch.Neuroimage. 2012; 59: 3611-3623Crossref PubMed Scopus (130) Google Scholar), parietal operculum (Mochizuki et al., 2009Mochizuki H. Inui K. Tanabe H.C. Akiyama L.F. Otsuru N. Yamashiro K. et al.Time course of activity in itch-related brain regions: a combined MEG–fMRI study.J Neurophysiol. 2009; 102: 2657-2666Crossref PubMed Scopus (63) Google Scholar, Papoiu et al., 2012Papoiu A.D. Coghill R.C. Kraft R.A. Wang H. Yosipovitch G. A tale of two itches. Common features and notable differences in brain activation evoked by cowhage and histamine induced itch.Neuroimage. 2012; 59: 3611-3623Crossref PubMed Scopus (130) Google Scholar), parahippocampal gyrus (Papoiu et al., 2012Papoiu A.D. Coghill R.C. Kraft R.A. Wang H. Yosipovitch G. A tale of two itches. Common features and notable differences in brain activation evoked by cowhage and histamine induced itch.Neuroimage. 2012; 59: 3611-3623Crossref PubMed Scopus (130) Google Scholar), and basal ganglia (Mochizuki et al., 2007Mochizuki H. Sadato N. Saito D.N. Toyoda H. Tashiro M. Okamura N. et al.Neural correlates of perceptual difference between itching and pain: a human fMRI study.Neuroimage. 2007; 36: 706-717Crossref PubMed Scopus (94) Google Scholar). However, the differences in brain processing of these two types of sensation have yet to be satisfactorily determined. The most significant advances in itch biology identifying itch-specific pathways have occurred in the peripheral nervous system, where there are itch-specific primary sensory neurons such as MrgprA3+ and NP2 (Dong and Dong, 2018Dong X. Dong X. Peripheral and central mechanisms of itch.Neuron. 2018; 98: 482-494Abstract Full Text Full Text PDF PubMed Scopus (164) Google Scholar). However, interneurons (GRP+) that relay itch input to the spinal cord of the central nervous system also receive pain sensory information (Sun et al., 2017Sun S. Xu Q. Guo C. Guan Y. Liu Q. Dong X. Leaky gate model: intensity-dependent coding of pain and itch in the spinal cord.Neuron. 2017; 93: 840-853.e5Abstract Full Text Full Text PDF PubMed Scopus (87) Google Scholar). Nevertheless, there are itch-specific GRPR+ interneurons in lamina I of the spinal cord, but projection neurons to the spinothalamic tract, thalamus, and beyond are polymodal (Hachisuka et al., 2016Hachisuka J. Baumbauer K.M. Omori Y. Snyder L.M. Koerber H.R. Ross S.E. Semi-intact ex vivo approach to investigate spinal somatosensory circuits.ELife. 2016; 5: e22866Crossref PubMed Scopus (3) Google Scholar), and thus decoding in the brain requires further exploration. To date, investigation of supraspinal processing of itch is limited and, as noted above, confined to a small number of imaging studies which show somatosensory, limbic, and motor-related activity similar to that evoked by noxious stimuli (for a detailed overview, see Lee et al., 2016Lee J.S. Han J.S. Lee K. Bang J. Lee H. The peripheral and central mechanisms underlying itch.BMB Rep. 2016; 49: 474-487Google Scholar). To contribute to our understanding of brain processing of itch compared with pain, we conducted activation likelihood estimation (ALE) meta-analysis of experimentally induced itch from the published fMRI literature and generated a comparison ALE map of experimental pain (using the previously reported coordinates of Tanasescu et al., 2016Tanasescu R. Cottam W.J. Condon L. Tench C.R. Auer D.P. Functional reorganisation in chronic pain and neural correlates of pain sensitisation: a coordinate based meta-analysis of 266 cutaneous pain fMRI studies.Neurosci Biobehav Rev. 2016; 68: 120-133Crossref PubMed Scopus (49) Google Scholar), to conduct meta-analytic conjunction/contrast analyses between the two sensations. Analyses were performed using Brainmap GingerALE, version 2.3.6 (Research Imaging Institute, San Antonio, TX). We adhered to the ALE method devised by Eickhoff et al., 2009Eickhoff S.B. Laird A.R. Grefkes C. Wang L.E. Zilles K. Fox P.T. Coordinate-based activation likelihood estimation meta-analysis of neuroimaging data: A random-effects approach based on empirical estimates of spatial uncertainty.Hum Brain Mapp. 2009; 30: 2907-2926Crossref PubMed Scopus (1303) Google Scholar, Eickhoff et al., 2012Eickhoff S.B. Bzdok D. Laird A.R. Kurth F. Fox P.T. Activation likelihood estimation meta-analysis revisited.Neuroimage. 2012; 59: 2349-2361Crossref PubMed Scopus (887) Google Scholar, with the correction devised by Turkeltaub et al., 2012Turkeltaub P.E. Eickhoff S.B. Laird A.R. Fox M. Wiener M. Fox P. Minimizing within-experiment and within-group effects in activation likelihood estimation meta-analyses.Hum Brain Mapp. 2012; 33: 1-13Crossref PubMed Scopus (731) Google Scholar. The P-values in our analyses were generated by 10,000 permutations. We used a cluster-level family-wise error correction at P < 0.05 to correct for multiple comparisons, following an initial cluster forming threshold of uncorrected P < 0.001 (see Supplementary Materials and Methods online for more information). ALE meta-analysis included all studies reporting whole brain fMRI analysis of experimentally induced itch (histamine, cowhage, or electrical stimulation). Data were pooled from a total of 11 experiments (from 10 papers, with a total of 117 participants and 313 reported foci) (Supplementary Figure S1). Significant clusters were observed in the thalamus, left frontal operculum cortex/insular cortex, and right frontal operculum cortex/insular cortex (Table 1, Figure 1).Table 1MNI Locations of Significant Clusters from the Itch ALE MapClusterBrain RegionPeak Voxel CoordinatesCluster Size (mm3)ALE Value (×10−2)No. of Contributing Experimentsxyzn%1Thalamus L-8-16103,9361.68763.640-1841.60-6-461.5710-421.36-8-14-21.31-10-18-81.202Frontal operculum / anterior insula / central operculum L-461222,0161.58545.45-3614-21.31-46281.25-54221.163Frontal operculum / anterior insula R401641,4241.72436.363810-21.33Abbreviations: ALE, activation likelihood estimation; L, left; MNI, Montreal Neurological Institute; R, rightCoordinates are reported in MNI space. Analysis used whole brain data from Herde et al., 2007Herde L. Forster C. Strupf M. Handwerker H.O. Itch induced by a novel method leads to limbic deactivations a functional MRI study.J Neurophysiol. 2007; 98: 2347-2356Crossref PubMed Scopus (82) Google Scholar, Ishiuji et al., 2009Ishiuji Y. Coghill R.C. Patel T.S. Oshiro Y. Kraft R.A. Yosipovitch G. Distinct patterns of brain activity evoked by histamine-induced itch reveal an association with itch intensity and disease severity in atopic dermatitis.Br J Dermatol. 2009; 161: 1072-1080Crossref PubMed Scopus (120) Google Scholar, Kleyn et al., 2012Kleyn C.E. McKie S. Ross A. Elliott R. Griffiths C.E. A temporal analysis of the central neural processing of itch.Br J Dermatol. 2012; 166: 994-1001Google Scholar, Leknes et al., 2007Leknes S.G. Bantick S. Willis C.M. Wilkinson J.D. Wise R.G. Tracey I. Itch and motivation to scratch: an investigation of the central and peripheral correlates of allergen- and histamine-induced itch in humans.J Neurophysiol. 2007; 97: 415-422Crossref PubMed Scopus (123) Google Scholar, Mochizuki et al., 2007Mochizuki H. Sadato N. Saito D.N. Toyoda H. Tashiro M. Okamura N. et al.Neural correlates of perceptual difference between itching and pain: a human fMRI study.Neuroimage. 2007; 36: 706-717Crossref PubMed Scopus (94) Google Scholar, Mochizuki et al., 2009Mochizuki H. Inui K. Tanabe H.C. Akiyama L.F. Otsuru N. Yamashiro K. et al.Time course of activity in itch-related brain regions: a combined MEG–fMRI study.J Neurophysiol. 2009; 102: 2657-2666Crossref PubMed Scopus (63) Google Scholar, Mochizuki et al., 2014Mochizuki H. Tanaka S. Morita T. Wasaka T. Sadato N. Kakigi R. The cerebral representation of scratching-induced pleasantness.J Neurophysiol. 2014; 111: 488-498Crossref PubMed Scopus (49) Google Scholar, Papoiu et al., 2012Papoiu A.D. Coghill R.C. Kraft R.A. Wang H. Yosipovitch G. A tale of two itches. Common features and notable differences in brain activation evoked by cowhage and histamine induced itch.Neuroimage. 2012; 59: 3611-3623Crossref PubMed Scopus (130) Google Scholar, Valet et al., 2008Valet M. Pfab F. Sprenger T. Wöller A. Zimmer C. Behrendt H. et al.Cerebral processing of histamine-induced itch using short-term alternating temperature modulation–an FMRI study.J Invest Dermatol. 2008; 128: 426-433Abstract Full Text Full Text PDF PubMed Scopus (82) Google Scholar, and Walter et al., 2005Walter B. Sadlo M.N. Kupfer J. Niemeier V. Brosig B. Stark R. et al.Brain activation by histamine prick test-induced itch.J Invest Dermatol. 2005; 125: 380-382Abstract Full Text Full Text PDF PubMed Scopus (50) Google Scholar. Studies that reported coordinates in the Talairach space were converted into MNI coordinates using GingerALE before analysis. Open table in a new tab Abbreviations: ALE, activation likelihood estimation; L, left; MNI, Montreal Neurological Institute; R, right Coordinates are reported in MNI space. Analysis used whole brain data from Herde et al., 2007Herde L. Forster C. Strupf M. Handwerker H.O. Itch induced by a novel method leads to limbic deactivations a functional MRI study.J Neurophysiol. 2007; 98: 2347-2356Crossref PubMed Scopus (82) Google Scholar, Ishiuji et al., 2009Ishiuji Y. Coghill R.C. Patel T.S. Oshiro Y. Kraft R.A. Yosipovitch G. Distinct patterns of brain activity evoked by histamine-induced itch reveal an association with itch intensity and disease severity in atopic dermatitis.Br J Dermatol. 2009; 161: 1072-1080Crossref PubMed Scopus (120) Google Scholar, Kleyn et al., 2012Kleyn C.E. McKie S. Ross A. Elliott R. Griffiths C.E. A temporal analysis of the central neural processing of itch.Br J Dermatol. 2012; 166: 994-1001Google Scholar, Leknes et al., 2007Leknes S.G. Bantick S. Willis C.M. Wilkinson J.D. Wise R.G. Tracey I. Itch and motivation to scratch: an investigation of the central and peripheral correlates of allergen- and histamine-induced itch in humans.J Neurophysiol. 2007; 97: 415-422Crossref PubMed Scopus (123) Google Scholar, Mochizuki et al., 2007Mochizuki H. Sadato N. Saito D.N. Toyoda H. Tashiro M. Okamura N. et al.Neural correlates of perceptual difference between itching and pain: a human fMRI study.Neuroimage. 2007; 36: 706-717Crossref PubMed Scopus (94) Google Scholar, Mochizuki et al., 2009Mochizuki H. Inui K. Tanabe H.C. Akiyama L.F. Otsuru N. Yamashiro K. et al.Time course of activity in itch-related brain regions: a combined MEG–fMRI study.J Neurophysiol. 2009; 102: 2657-2666Crossref PubMed Scopus (63) Google Scholar, Mochizuki et al., 2014Mochizuki H. Tanaka S. Morita T. Wasaka T. Sadato N. Kakigi R. The cerebral representation of scratching-induced pleasantness.J Neurophysiol. 2014; 111: 488-498Crossref PubMed Scopus (49) Google Scholar, Papoiu et al., 2012Papoiu A.D. Coghill R.C. Kraft R.A. Wang H. Yosipovitch G. A tale of two itches. Common features and notable differences in brain activation evoked by cowhage and histamine induced itch.Neuroimage. 2012; 59: 3611-3623Crossref PubMed Scopus (130) Google Scholar, Valet et al., 2008Valet M. Pfab F. Sprenger T. Wöller A. Zimmer C. Behrendt H. et al.Cerebral processing of histamine-induced itch using short-term alternating temperature modulation–an FMRI study.J Invest Dermatol. 2008; 128: 426-433Abstract Full Text Full Text PDF PubMed Scopus (82) Google Scholar, and Walter et al., 2005Walter B. Sadlo M.N. Kupfer J. Niemeier V. Brosig B. Stark R. et al.Brain activation by histamine prick test-induced itch.J Invest Dermatol. 2005; 125: 380-382Abstract Full Text Full Text PDF PubMed Scopus (50) Google Scholar. Studies that reported coordinates in the Talairach space were converted into MNI coordinates using GingerALE before analysis. Significant clusters resulting from experimental pain meta-analysis are fully described by Tanasescu et al., 2016Tanasescu R. Cottam W.J. Condon L. Tench C.R. Auer D.P. Functional reorganisation in chronic pain and neural correlates of pain sensitisation: a coordinate based meta-analysis of 266 cutaneous pain fMRI studies.Neurosci Biobehav Rev. 2016; 68: 120-133Crossref PubMed Scopus (49) Google Scholar; therefore, our ALE map of experimental pain was used only in the conjunction and contrast analysis described next. The conjunction analysis between itch and pain showed three significant clusters, located in the left thalamus and the left and right frontal operculum/insula. We chose a minimum cluster size of 500 mm3 for contrast analyses. For itch – pain, we identified five clusters: left and right thalamus, left anterior insula/frontal operculum, right central operculum, and right supramarginal gyrus. The reverse pain – itch contrast revealed four clusters: right parietal operculum/postcentral gyrus, right frontal pole (inferior frontal gyrus), left frontal pole (middle frontal gyrus), and right supramarginal gyrus. Experimental itch was associated with activations in the thalamus and anterior parts of the left and right insula/frontal operculum. There was a high degree of overlap in brain activation for itch and pain in the conjunction analysis. However, areas of the thalamus, anterior insula/frontal operculum, central operculum, and supramarginal gyrus showed significant differences in activation convergence in an itch – pain contrast. This finding suggests that somatosensory processing that is specific to itch resides in these areas, but further work is necessary to resolve this possibility with precision. Our meta-analysis confirms that the thalamus is the most consistently activated brain region in fMRI studies of experimental itch (Herde et al., 2007Herde L. Forster C. Strupf M. Handwerker H.O. Itch induced by a novel method leads to limbic deactivations a functional MRI study.J Neurophysiol. 2007; 98: 2347-2356Crossref PubMed Scopus (82) Google Scholar, Leknes et al., 2007Leknes S.G. Bantick S. Willis C.M. Wilkinson J.D. Wise R.G. Tracey I. Itch and motivation to scratch: an investigation of the central and peripheral correlates of allergen- and histamine-induced itch in humans.J Neurophysiol. 2007; 97: 415-422Crossref PubMed Scopus (123) Google Scholar, Mochizuki et al., 2009Mochizuki H. Inui K. Tanabe H.C. Akiyama L.F. Otsuru N. Yamashiro K. et al.Time course of activity in itch-related brain regions: a combined MEG–fMRI study.J Neurophysiol. 2009; 102: 2657-2666Crossref PubMed Scopus (63) Google Scholar, Mochizuki et al., 2014Mochizuki H. Tanaka S. Morita T. Wasaka T. Sadato N. Kakigi R. The cerebral representation of scratching-induced pleasantness.J Neurophysiol. 2014; 111: 488-498Crossref PubMed Scopus (49) Google Scholar, Papoiu et al., 2012Papoiu A.D. Coghill R.C. Kraft R.A. Wang H. Yosipovitch G. A tale of two itches. Common features and notable differences in brain activation evoked by cowhage and histamine induced itch.Neuroimage. 2012; 59: 3611-3623Crossref PubMed Scopus (130) Google Scholar, Valet et al., 2008Valet M. Pfab F. Sprenger T. Wöller A. Zimmer C. Behrendt H. et al.Cerebral processing of histamine-induced itch using short-term alternating temperature modulation–an FMRI study.J Invest Dermatol. 2008; 128: 426-433Abstract Full Text Full Text PDF PubMed Scopus (82) Google Scholar), and corroborates positron-emission tomography imaging studies that highlight the thalamus as important in the subjective appraisal of itch (Mochizuki et al., 2003Mochizuki H. Tashiro M. Kano M. Sakurada Y. Itoh M. Yanai K. Imaging of central itch modulation in the human brain using positron emission tomography.Pain. 2003; 105: 339-346Abstract Full Text Full Text PDF PubMed Scopus (187) Google Scholar). As with itch, the thalamus is acknowledged as a critical area involved in the perception of pain, being consistently reported in meta-analyses of fMRI studies on experimental pain (Jensen et al., 2016Jensen K.B. Regenbogen C. Ohse M.C. Frasnelli J. Freiherr J. Lundström J.N. Brain activations during pain: a neuroimaging meta-analysis of patients with pain and healthy controls.Pain. 2016; 157: 1279-1286Crossref PubMed Scopus (70) Google Scholar, Tanasescu et al., 2016Tanasescu R. Cottam W.J. Condon L. Tench C.R. Auer D.P. Functional reorganisation in chronic pain and neural correlates of pain sensitisation: a coordinate based meta-analysis of 266 cutaneous pain fMRI studies.Neurosci Biobehav Rev. 2016; 68: 120-133Crossref PubMed Scopus (49) Google Scholar). Our conjunction analysis showed substantial overlap between itch and pain in the thalamus, with every itch brain region overlapping with pain regions. However, areas of the left and right thalamus showed significant differences in convergence between itch and pain, supporting the proposals that variation in itch and pain perception can found in subregions of the thalamus (Drzezga et al., 2001Drzezga A. Darsow U. Treede R.D. Siebner H. Frisch M. Munz F. et al.Central activation by histamine-induced itch: analogies to pain processing: a correlational analysis of O-15 H2O positron emission tomography studies.Pain. 2001; 92: 295-305Abstract Full Text Full Text PDF PubMed Scopus (214) Google Scholar, Mochizuki et al., 2003Mochizuki H. Tashiro M. Kano M. Sakurada Y. Itoh M. Yanai K. Imaging of central itch modulation in the human brain using positron emission tomography.Pain. 2003; 105: 339-346Abstract Full Text Full Text PDF PubMed Scopus (187) Google Scholar), and that differences in thalamus sensitivity underlie the difference between the sensations (Mochizuki et al., 2007Mochizuki H. Sadato N. Saito D.N. Toyoda H. Tashiro M. Okamura N. et al.Neural correlates of perceptual difference between itching and pain: a human fMRI study.Neuroimage. 2007; 36: 706-717Crossref PubMed Scopus (94) Google Scholar). Clearly, convergence and divergence of thalamic activation in itch and pain are complex and require further investigation. The remaining two significant clusters from the itch ALE comprised bilateral activity in anterior parts of the insula and the frontal operculum area of the insula, confirming that these areas are consistently activated across studies of experimental itch (Herde et al., 2007Herde L. Forster C. Strupf M. Handwerker H.O. Itch induced by a novel method leads to limbic deactivations a functional MRI study.J Neurophysiol. 2007; 98: 2347-2356Crossref PubMed Scopus (82) Google Scholar, Leknes et al., 2007Leknes S.G. Bantick S. Willis C.M. Wilkinson J.D. Wise R.G. Tracey I. Itch and motivation to scratch: an investigation of the central and peripheral correlates of allergen- and histamine-induced itch in humans.J Neurophysiol. 2007; 97: 415-422Crossref PubMed Scopus (123) Google Scholar, Mochizuki et al., 2009Mochizuki H. Inui K. Tanabe H.C. Akiyama L.F. Otsuru N. Yamashiro K. et al.Time course of activity in itch-related brain regions: a combined MEG–fMRI study.J Neurophysiol. 2009; 102: 2657-2666Crossref PubMed Scopus (63) Google Scholar, Mochizuki et al., 2014Mochizuki H. Tanaka S. Morita T. Wasaka T. Sadato N. Kakigi R. The cerebral representation of scratching-induced pleasantness.J Neurophysiol. 2014; 111: 488-498Crossref PubMed Scopus (49) Google Scholar, Papoiu et al., 2012Papoiu A.D. Coghill R.C. Kraft R.A. Wang H. Yosipovitch G. A tale of two itches. Common features and notable differences in brain activation evoked by cowhage and histamine induced itch.Neuroimage. 2012; 59: 3611-3623Crossref PubMed Scopus (130) Google Scholar). These areas are also commonly activated by pain (Yosipovitch and Mochizuki, 2015Yosipovitch G. Mochizuki H. Neuroimaging of itch as a tool of assessment of chronic itch and its management.Handb Exp Pharmacol. 2015; 226: 57-70Crossref Scopus (21) Google Scholar, Jensen et al., 2016Jensen K.B. Regenbogen C. Ohse M.C. Frasnelli J. Freiherr J. Lundström J.N. Brain activations during pain: a neuroimaging meta-analysis of patients with pain and healthy controls.Pain. 2016; 157: 1279-1286Crossref PubMed Scopus (70) Google Scholar, Tanasescu et al., 2016Tanasescu R. Cottam W.J. Condon L. Tench C.R. Auer D.P. Functional reorganisation in chronic pain and neural correlates of pain sensitisation: a coordinate based meta-analysis of 266 cutaneous pain fMRI studies.Neurosci Biobehav Rev. 2016; 68: 120-133Crossref PubMed Scopus (49) Google Scholar), and this was confirmed by our conjunction analysis. The insula is understood to process stimulus intensity in both pain and itch. For example, Papoiu et al., 2012Papoiu A.D. Coghill R.C. Kraft R.A. Wang H. Yosipovitch G. A tale of two itches. Common features and notable differences in brain activation evoked by cowhage and histamine induced itch.Neuroimage. 2012; 59: 3611-3623Crossref PubMed Scopus (130) Google Scholar reported correlations between itch intensity and insula activity. Additionally, the anterior insula is associated with affective responses to stimuli, which may relate to the high rates of depression in atopic dermatitis (Gupta and Gupta, 1998Gupta M.A. Gupta A.K. Depression and suicidal ideation in dermatology patients with acne, alopecia areata, atopic dermatitis and psoriasis.Br J Dermatol. 1998; 139: 846-850Crossref PubMed Scopus (709) Google Scholar). It is the affective component of itch which has led to the suggestion that psychological interventions, such as mindfulness or cognitive behavioral therapy, could prove successful in chronic itch treatment (Schut et al., 2014Schut C. Bosbach S. Gieler U. Kupfer J. Personality traits, depression and itch in patients with atopic dermatitis in an experimental setting: a regression analysis.Acta Derm Venereol. 2014; 94: 20-25Crossref PubMed Scopus (57) Google Scholar). Psychological interventions that reduce stress may produce positive effects on itch, as well as altering itch-associated brain activation, such as connectivity between the insular cortex and the anterior cingulate cortex (Mochizuki et al., 2017Mochizuki H. Schut C. Nattkemper L.A. Yosipovitch G. Brain mechanism of itch in atopic dermatitis and its possible alteration through non-invasive treatments.Allergol Int. 2017; 66: 14-21Abstract Full Text Full Text PDF PubMed Scopus (35) Google Scholar). The pain – itch subtraction showed residual activation in the parietal operculum and postcentral gyrus that seems to be specific to pain. Possibly, pain activates somatosensory cortices more reliably than itch, as is indicated by molecular imaging studies (Mochizuki et al., 2003Mochizuki H. Tashiro M. Kano M. Sakurada Y. Itoh M. Yanai K. Imaging of central itch modulation in the human brain using positron emission tomography.Pain. 2003; 105: 339-346Abstract Full Text Full Text PDF PubMed Scopus (187) Google Scholar, Darsow et al., 2000Darsow U. Drzezga A. Frisch M. Munz F. Weilke F. Bartenstein P. et al.Processing of histamine-induced itch in the human cerebral cortex: a correlation analysis with dermal reactions.J Invest Dermatol. 2000; 115: 1029-1033Abstract Full Text Full Text PDF PubMed Scopus (130) Google Scholar, Drzezga et al., 2001Drzezga A. Darsow U. Treede R.D. Siebner H. Frisch M. Munz F. et al.Central activation by histamine-induced itch: analogies to pain processing: a correlational analysis of O-15 H2O positron emission tomography studies.Pain. 2001; 92: 295-305Abstract Full Text Full Text PDF PubMed Scopus (214) Google Scholar). The main limitation of the present analyses is our focus on experimentally induced itch in healthy individuals. However, the strength of this approach is that confounding factors such as comorbidity are carefully controlled. It is probable that chronic and acute itch differ in central nervous system activity, and our findings therefore require validation with data from clinical populations. In addition, our analysis combined data from several different experimental itch methodologies. It may be that there are different types of itch, each with a distinct neural signature. The fundamental studies to explore this possibility have yet to be conducted, and the quantity of data on neural correlates of itch is currently insufficient to independently investigate specific types of itch with meta-analysis. We report that the thalamus and the affective areas of the anterior insula/frontal operculum are consistently activated across fMRI studies that induce itch experimentally. We propose these brain regions as targets for future exploratory neurofeedback experimentation. Data used in main analysis and supplementary analysis have been submitted with this manuscript as Supplementary Data online. These are available for replication, and building upon the current analysis. CAR, AS, NF, and TCK report grants from Unilever during the conduct of this study. TG and AT are employees of Unilever. This work was funded by Unilever. TG and AT are employees of Unilever, which markets personal care products including Dove DermaSeries. Conceptualization: CAR, TG; Formal Analysis: CAR; Funding Acquisition: TCK; Investigation: CAR; Methodology: CAR; Validation: NF; Writing - Original Draft Preparation: CAR; Writing - Review and Editing: CAR, TG, AS, NF, AT, TCK Systematic searches using three databases (MEDLINE, Scopus, and PsycINFO) were conducted using the following MeSH search terms: (fMRI AND [itch OR pruritus]) and (fMRI AND [affective touch OR pleasant touch]). Searches were restricted to terms found in the title or abstract of the articles. No date limit was set for the searches. We adhered to the Preferred Reporting Items for Systematic Reviews and Meta-analysis method (Supplementary Table S2; http://www.prisma-statement.org). Generic inclusion criteria were the following: (i) human functional magnetic resonance imaging (fMRI) studies published up until February 2018; (ii) original articles reported in English; (iii) published in peer-reviewed journals; (iv) fMRI coordinates reported in the paper or supplementary material in either Montreal Neurological Institute (Evans et al., 1993Evans A.C. Collins D.L. Mills S.R. Brown E.D. Kelly R.L. Peters T.M. 3D statistical neuroanatomical models from 305 MRI volumes. In: Nuclear Science Symposium and Medical Imaging Conference, 1993 IEEE Conference Record..IEEE;. 1993; (p. 1813–7.)Google Scholar) or Talairach space (Talairach and Tournoux, 1988Talairach J. Tournoux P. Co-planar stereotaxic atlas of the human brain.3-Dimensional proportional system: an approach to cerebral imaging. Thieme, New York1988Google Scholar); (v) data were obtained from a healthy population (systemic disease-free); and (vi) analyses were conducted on whole brain fMRI data (region of interest analy

Abstract Expectations can affect subjective sensory and hedonic ratings of tastes, but it is unclear whether they also shape sensory experience at a perceptual level. The neural correlates of the taste‐expectancy relationship were explored through EEG analysis. Using a trial‐by‐trial cueing paradigm, lingual delivery of 0.05 M or 0.3 M sucrose solutions was preceded by congruent or incongruent visual cues designed to promote anticipation of either a low‐sweet or high‐sweet solution. When participants were cued to expect low‐sweet, but received high‐sweet (incongruent cue), intensity ratings for high‐sweet decreased. Likewise, expectation of high‐sweet increased intensity ratings of low‐sweet solutions. Taste‐dependent, right central‐parietal gustatory ERPs were detected, with greater P1 (associated with greater right insula activation) and P2 peak amplitudes for high‐sweet tastes. Valid cue‐taste pairings led to specific reduced right‐lateralized N400 responses (associated with an attenuation in right insula activation) compared with invalid cue‐taste pairings. Finally, P1 amplitudes following invalidly cued low‐sweet tastes closely matched those generated by expected high‐sweet tastes, and P1 amplitudes for invalidly cued high‐sweet tastes resembled those generated by low‐sweet tastes. We conclude that, as well as modifying subjective ratings toward the anticipated intensity level, expectations affect cortical activity in a top‐down manner to induce bidirectional assimilation in the early perceptual processing of sweet taste and modulate N400 ERP components not previously associated with gustatory stimulation.

Implicit attentional processes are biased toward food-related stimuli, with the extent of that bias reflecting relative motivation to eat. These interactions have typically been investigated by comparisons between fasted and sated individuals. In this study, temporal changes in implicit attention to food were assessed in relation to natural, spontaneous changes in appetite occurring before and after an anticipated midday meal. Non-fasted adults performed an emotional blink of attention (EBA) task at intervals, before and after consuming preferred, pre-selected sandwiches to satiety. Participants were required to detect targets within a rapid visual stream, presented after task-irrelevant food (preferred or non-preferred sandwiches, or desserts) or non-food distractor images. All categories of food distractor preferentially captured attention even when appetite levels were low, but became more distracting as appetite increased preprandially, reducing task accuracy maximally as hunger peaked before lunch. Postprandially, attentional capture was markedly reduced for images of the specific sandwich type consumed and, to a lesser extent, for images of other sandwich types that had not been eaten. Attentional capture by images of desserts was unaffected by satiation. These findings support an important role of selective visual attention in the guidance of motivated behaviour. Naturalistic, meal-related changes in appetite are accompanied by changes in implicit attention to visual food stimuli that are easily detected using the EBA paradigm. Preprandial enhancement of attention capture by food cues likely reflects increases in the incentive motivational value of all food stimuli, perhaps providing an implicit index of wanting. Postprandial EBA responses confirm that satiation on a particular food results in relative inattention to that food, supporting an important attentional component in the operation of sensory-specific satiety.

Background: The prevalence of obesity has increased dramatically in recent years. As exposure to obesity increases, perceptions of what is a ‘normal’ weight are likely to change and this may result in overweight and obese people being perceived as healthier weights than they actually are. We tested whether exposure to obesity results in individuals being more likely to perceive an overweight person as being of healthy weight and whether this would impact upon evaluations of whether an overweight person should consider losing weight. Methods: Across three experiments with over 350 participants, we examined the effect that exposing participants to photographs of either obese or healthy weight young males had on visual judgements of whether an overweight young male was of healthy weight. We also tested whether exposure influenced participants’ perceptions of what a ‘normal’ weight is, as we predicted that this might mediate the effect that obesity exposure has on weight perceptions. Results: In all studies, exposure to obesity resulted in an overweight male being perceived to be of healthier weight. There was also evidence that this effect was explained by changes to perceptions of what is a ‘normal’ weight (Experiment 2). Obesity exposure also resulted in participants being more likely to believe that an overweight person did not need to consider losing weight (Experiment 3). Conclusions: These findings provide causal evidence that perceptions of weight and health status are strongly influenced by the body weight of the people we see around us.

Considerable effort has been made in recent years to unravel the mechanisms by which motivational and affective processes impact on behaviour and reasoning. Recent research shows that attentional processing is strongly influenced by motivational states, such as appetite. However, little has been done to investigate how affective processes influence attentional selection with naturally occurring stimuli, which is motivationally arousing. This study utilised an adapted version of Piech et al’s (2010) emotional blink of attention (EBA) paradigm by using affective priming to investigate to effect of positive affect on attentional capture. Participants (n = 30) were required to detect targets appearing in a rapid stream of visually presented stimuli, after different types of distractors irrelevant to the task. Findings show that food stimuli were captured to a greater extent following priming of positive affect within the visual streams. The study demonstrates that EBA’s may be manipulated to alter affective state and measure its influence on motivationally arousing stimuli, though the opposite may also be possible.

BACKGROUND AND PURPOSE Endocannabinoid systems are strongly implicated in the physiological control of appetite and eating behaviour, with cannabinoid CB1 receptor agonists and antagonists, respectively, increasing or decreasing food intake. This study examined the acute actions of the putative endocannabinoid noladin ether on food intake and eating motivation, assessing how it affects the amount of work expended by animals to obtain food.EXPERIMENTAL APPROACH Non‐deprived male rats were injected systemically with noladin ether to assess its acute effects on ad libitum feeding of a standard laboratory diet. Additionally, the effects of noladin on lever pressing for palatable food were determined using a progressive ratio (PR) operant paradigm.KEY RESULTS Noladin dose dependently increased 2 h food intake, with a significant effect over 1 h after a dose of 0.5 mg·kg−1. In the PR test, this hyperphagic dose of noladin ether promoted sustained high rates of responding and significantly increased the total number of lever presses and break‐point. These latter effects were prevented by pretreatment with 1.0 mg·kg−1 of the selective CB1 antagonist surinabant (SR147778), that alone had no effect on responding.CONCLUSIONS AND IMPLICATIONS This is the first report of hyperphagia induced by acute noladin administration, and the first description of behavioural actions in rats. Consistent with prevailing notions about the role of endocannabinoids in appetite, a hyperphagic dose of noladin markedly increased efforts expended by animals to obtain food. Thus, noladin exerts a specific action on eating motivation; possibly promoting eating by increasing the incentive value of food.

Objective. To provide the most comprehensive analysis to date of the extent of food advertising on UK television channels popular with young people following regulatory reform of this type of marketing activity. Methods. UK television was recorded 06:00-22:00 h for a weekday and a weekend day every month between January and December 2008 for 14 of the most popular commercial channels broadcasting children's/family viewing. Recordings were screened for advertisements, which were coded according to predefined categories including whether they were broadcast in peak/non-peak children's viewing time. Food advertisements were coded as core (healthy)/non-core (unhealthy)/miscellaneous foods. Results. Food and drinks were the third most heavily advertised product category, and there were a significantly greater proportion of advertisements for food/drinks during peak compared to non-peak children's viewing times. A significantly greater proportion of the advertisements broadcast around soap operas than around children's programmes were for food/drinks. Children's channels broadcast a significantly greater proportion of non-core food advertisements than the family channels. There were significant differences between recording months for the proportion of core/non-core/miscellaneous food advertisements. Conclusions. Despite regulation, children in the UK are exposed to more TV advertising for unhealthy than healthy food items, even at peak children's viewing times. There remains scope to strengthen the rules regarding advertising of HFSS foods around programming popular with children and adults alike, where current regulations do not apply. Ongoing, systematic monitoring is essential for evaluation of the effectiveness of regulations designed to reduce children's exposure to HFSS food advertising on television in the UK.

OBJECTIVE: Our aim was to determine if levels of television viewing (a proxy measure for habitual commercial exposure) affect children's food preference responses to television food commercials. METHODS: A total of 281 children aged 6 to 13 years from northwest England viewed toy or food television commercials followed by a cartoon on 2 separate occasions; they then completed 3 food preference measures, a commercial recognition task, and a television viewing questionnaire. RESULTS: After viewing the food commercials, all children selected more branded and nonbranded fat-rich and carbohydrate-rich items from food preference checklists compared with after viewing the toy commercials. The food preferences of children with higher habitual levels of television viewing were more affected by food commercial exposure than those of low television viewers. After viewing food commercials, high television viewing children selected a greater number of branded food items compared with after the toy commercials as well as compared with the low television viewers. Children correctly recognized more food commercials than toy commercials. CONCLUSIONS: Exposure to television food commercials enhanced high television viewers' preferences for branded foods and increased reported preferences for all food items (branded and nonbranded) relative to the low television viewers. This is the first study to demonstrate that children with greater previous exposure to commercials (high television viewers) seemed to be more responsive to food promotion messages than children with lower previous advertising exposure.

The aim of this study was to quantify the nature and extent of use of persuasive marketing techniques in television advertisements (adverts) to promote foods to children. Popular UK commercial television channels broadcasting children's/family viewing were recorded for 2 days (6 am-10 pm) every month in 2008 and recordings were screened for adverts. Eighteen thousand eight hundred and eighty eight adverts were for food and these were coded for peak/non-peak children's viewing time and representation of core (healthy)/non-core (unhealthy)/miscellaneous foods. The analysis assessed use of persuasive appeals, premium offers, promotional characters (brand equity and licensed characters), celebrity endorsers and website promotion in food adverts. Promotional characters, celebrity endorsers and premium offers were used more frequently to promote non-core than core foods, even on dedicated children's channels. Brand equity characters featured on a greater proportion of food adverts than licensed characters. A food brand website was promoted in a third of food adverts (websites are not covered by the statutory regulation on food advertising). This extensive analysis of television adverts demonstrated that the use of persuasive marketing techniques to promote unhealthy foods was extensive in broadcasting popular with children despite regulations. Further studies should incorporate an analysis of the content of websites promoted during food adverts.