Afferents of the large, electrically 'silent' frontal cortex in an egg-laying mammal, the echidna, were studied with the somatopetal axonal transport technique. This cortical area receives thalamic projections only from the anterior part of the anteromediodorsal region. The medial parts of the cortex receive afferents from more medial neurons, whereas the lateral area is innervated from the laterally placed perikarya of this thalamic region. The nonthalamic afferents to the frontal cortex are, with few exceptions, similar to the afferents of the prefrontal cortex in placental mammals. Cortical afferents originate in all layers of the contralateral symmetrical areas and in the ipsilateral paleocortex, especially the cortex in the bottom of the sulcus mu. The claustrum could not be identified, neither cytoarchitecturally nor hodologically. Pending confirmation from studies of the diencephalon, we presently conclude that the large anterior cortical area in this species corresponds to the prefrontal cortex of eutherian mammals. If this conclusion is correct, the echidna is the only species studied to date that has a proportionally larger prefrontal cortex than humans.

In two echidnas injections of radioactively labeled amino acids were made into the cortical area which has been shown to receive afferents from the anteromediodorsal region of the thalamus and which is therefore tentatively identified as the prefrontal cortex. Efferents were found in the symmetrical area of the contralateral cortex, in the paleocortex and neostriatum bilaterally, the ipsilateral anteromediodorsal region of the thalamus, the hypothalamus, the ventral tegmental area, and the pons. No evidence was found of efferents caudal to the pons. The axons reached the contralateral side via the anterior commissure. The innervation of the cortex was columnar and that of the neostriatum patchy, as was previously demonstrated for comparable projections in placental mammals. The present material, albeit limited, shows some remarkable similarities between prefrontal efferents in the echidna and the placental mammals, including Old World monkeys.

Scandinavian Journal of ImmunologyVolume 15, Issue s9 p. 223-240 Synaptic Membrane Proteins in Mammalian Brain E. BOCK, E. BOCK The Protein Laboratory; Institute of Neurophysiology, Panum Institute; Institute of Medical Microbiology; and Department of Physiology C, Panum Institute; University of Copenhagen, Copenhagen, DenmarkSearch for more papers by this authorI. DIVAC, I. DIVAC The Protein Laboratory; Institute of Neurophysiology, Panum Institute; Institute of Medical Microbiology; and Department of Physiology C, Panum Institute; University of Copenhagen, Copenhagen, DenmarkSearch for more papers by this authorB. NORRILD, B. NORRILD The Protein Laboratory; Institute of Neurophysiology, Panum Institute; Institute of Medical Microbiology; and Department of Physiology C, Panum Institute; University of Copenhagen, Copenhagen, DenmarkSearch for more papers by this authorN. A. THORN, N. A. THORN The Protein Laboratory; Institute of Neurophysiology, Panum Institute; Institute of Medical Microbiology; and Department of Physiology C, Panum Institute; University of Copenhagen, Copenhagen, DenmarkSearch for more papers by this authorC. TORP-PEDERSEN, C. TORP-PEDERSEN The Protein Laboratory; Institute of Neurophysiology, Panum Institute; Institute of Medical Microbiology; and Department of Physiology C, Panum Institute; University of Copenhagen, Copenhagen, DenmarkSearch for more papers by this authorM. TREIMAN, M. TREIMAN The Protein Laboratory; Institute of Neurophysiology, Panum Institute; Institute of Medical Microbiology; and Department of Physiology C, Panum Institute; University of Copenhagen, Copenhagen, DenmarkSearch for more papers by this author E. BOCK, E. BOCK The Protein Laboratory; Institute of Neurophysiology, Panum Institute; Institute of Medical Microbiology; and Department of Physiology C, Panum Institute; University of Copenhagen, Copenhagen, DenmarkSearch for more papers by this authorI. DIVAC, I. DIVAC The Protein Laboratory; Institute of Neurophysiology, Panum Institute; Institute of Medical Microbiology; and Department of Physiology C, Panum Institute; University of Copenhagen, Copenhagen, DenmarkSearch for more papers by this authorB. NORRILD, B. NORRILD The Protein Laboratory; Institute of Neurophysiology, Panum Institute; Institute of Medical Microbiology; and Department of Physiology C, Panum Institute; University of Copenhagen, Copenhagen, DenmarkSearch for more papers by this authorN. A. THORN, N. A. THORN The Protein Laboratory; Institute of Neurophysiology, Panum Institute; Institute of Medical Microbiology; and Department of Physiology C, Panum Institute; University of Copenhagen, Copenhagen, DenmarkSearch for more papers by this authorC. TORP-PEDERSEN, C. TORP-PEDERSEN The Protein Laboratory; Institute of Neurophysiology, Panum Institute; Institute of Medical Microbiology; and Department of Physiology C, Panum Institute; University of Copenhagen, Copenhagen, DenmarkSearch for more papers by this authorM. TREIMAN, M. TREIMAN The Protein Laboratory; Institute of Neurophysiology, Panum Institute; Institute of Medical Microbiology; and Department of Physiology C, Panum Institute; University of Copenhagen, Copenhagen, DenmarkSearch for more papers by this author First published: November 1982 https://doi.org/10.1111/j.1365-3083.1982.tb03766.xCitations: 5AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume15, Issues9November 1982Pages 223-240 RelatedInformation

Thirteen rhesus monkeys were trained to perform delayed alternation and visual discrimination tasks and intraventricular cannulas were implanted. The animals were divided in three groups: injected with anti-caudate nucleus; antihippocampal; and normal gamma globulin, respectively. They were then tested for retention. The anti-caudate and anti-hippocampal groups were significantly impaired in the delayed alternation performance as compared to the nromal gamma globulin group. The impairment was temporary. No group was impaired on visual discrimination presented along the delayed alternation task.

IN a vast literature on learning and retention there are, surprisingly, no data concerning effects of experimentally controlled hibernation. In contrast, experiments to investigate the effects of hypothermia are increasing. Andjus et al.1 have shown that retention is unimpaired after hypothermia even in animals cooled to near 0° C. On the other hand, initial learning, investigated after recovery from hypothermia, has been most frequently found to be significantly impaired in subjects whose body temperature has been lowered to 0°–5° C, but unaffected in subjects cooled to 13°–32° C1. In general, the longer the time between recovering from hypothermia and the beginning of learning, the smaller was the impairment observed (paper presented by N. Mrosovsky to the third International Symposium on Natural Mammalian Hibernation in Toronto in 1965).