Comparison of the cortical degeneration in the visual regions of the temporal lobe of the monkey following section of the anterior commissure and the splenium

Zeki, Semir

doi:10.1002/cne.901480204

Cited by 89 publications

(9 citation statements)

References 17 publications

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“…The septal nuclei, the fornix, and the underlying diencephalic structures were spared. This surgery disconnected the anterior temporal cortex of each hemisphere from the other, since most commissural fibers of this area traverse the AC rather than the corpus callosum (20)(21)(22). After recovery, the monkey was trained with a set (set A) of the paired associates to the criterion performance level, and then extracellular spike discharges of single neurons were recorded as a prelesion control in the anterior IT cortex (9,23,24).…”

Section: Resultsmentioning

confidence: 99%

“…We combined single-unit recording techniques with surgical manipulations in the monkey. First, the AC of the monkeys was cut to remove influences upon anterior IT neurons from those in the other hemisphere (20)(21)(22). Behaviorally, the monkeys fixated the stimuli and learned the pair-association task quite normally, just as in the previous study (9).…”

Section: Discussionmentioning

confidence: 99%

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Formation of mnemonic neuronal responses to visual paired associates in inferotemporal cortex is impaired by perirhinal and entorhinal lesions.

Higuchi

Miyashita

1996

Proc. Natl. Acad. Sci. U.S.A.

250

178

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Functional roles of the cortical backward signal in long-term memory formation were studied in monkeys performing a visual pair-association task Before the monkeys learned the task, the anterior commissure was transected, disconnecting the anterior temporal cortex of each hemisphere. After training with 12 pairs of pictures, single units were recorded from the inferotemporal cortex of the monkeys as the control. By injecting a grid of ibotenic acid, we unilaterally lesioned the entorhinal and perirhinal cortex, which provides massive direct and indirect backward projections ipsilaterally to the inferotemporal cortex. After the lesion, the monkeys fixated the cue stimulus normally, relearned the preoperatively learned set (set A), and learned a new set (set B) of paired associates. Then, single units were recorded from the same area as for the prelesion control. We found that (i) in spite of the lesion, the sampled neurons responded strongly and selectively to both the set A and set B patterns and (ii) the paired associates elicited significantly correlated responses in the control neurons before the lesion but not in the cells tested after the lesion, either for set A or set B stimuli. We conclude that the ability of inferotemporal neurons to represent association between picture pairs was lost after the lesion of entorhinal and perirhinal cortex, most likely through disruption of backward neural signals to the inferotemporal neurons, while the ability of the neurons to respond to a particular visual stimulus was left intact.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Formation of mnemonic neuronal responses to visual paired associates in inferotemporal cortex is impaired by perirhinal and entorhinal lesions.

Higuchi

Miyashita

1996

Proc. Natl. Acad. Sci. U.S.A.

250

178

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“…Although similar functions are performed by the corpus callosum, cortical areas served by these two commissures have in some cases been found to be distinct (58). The unique use of the anterior commissure as an extracallosal commissural pathway would probably not provide the level of compensation generally seen in acallosals, and it seems likely that the use of several other commissures is also enhanced (35).…”

Section: Discussionmentioning

confidence: 99%

Increased Axon Number in the Anterior Commissure of Mice Lacking a Corpus Callosum

Livy

Schalomon

Roy

et al. 1997

Experimental Neurology

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Abstract:Relatively few behavioral deficits are apparent in subjects with hereditary absence of the corpus callosum (CC). The anterior commissure (AC) has been suggested to provide an extracallosal route for the transfer of interhemispheric information in subjects with this congenital defect. Anterior commissure size, axon number, axon diameter, and neuronal distribution were compared between normal mice and those with complete CC absence. No difference in midsagittal AC area was found between normals and acallosals, nor were differences found in the numbers or diameters of myelinated axons. However, axon counts indicated an 17%increase or about 70,000 more unmyelinated axons in the AC of acallosal mice, and the mean diameter of unmyelinated axons was slightly less than in normal mice (0.24 vs 0.26 μm). This decrease in axon diameter enabled more axons to pass through the AC without increasing its midsagittal area. The topographical distribution of neurons sending axons through the AC, assessed with lipophilic dyes, was qualitatively similar for almost all the known regions of origin of the anterior commissure in normal and acallosal mice. There was a pronounced deficit of AC cells in the anterior piriform cortex of BALB/c mice, but this occurred whether or not the mouse suffered absent CC. Although the increase in AC axon number is far smaller than the number of CC axons that fail to reach the opposite hemisphere, the higher number of axons present in the AC of acallosal mice may contribute to the functional compensation for the loss of the CC.

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“…Not surprisingly, we found that the distribution of callosal projection cells is very similar to that of callosal fiber terminations and thus reflects topographic organization to the same degree in various regions of cortex. The major dissimilarity in callosal inputs versus outputs is in inferotemporal cortex: this region receives inputs via the corpus callosum and, in its anterior portion, via the anterior commissure (Zeki, 1973), but its projections to the contralateral hemisphere pass predominantly through the anterior commissure and not the corpus callosum (Jouandet and Gazzaniga, 1979;Hamilton, 1982; see Fig. 10).…”

Section: Discussionmentioning

confidence: 99%

“…Within IT, however, there are regional differences in architecture (Seltzer and Pandya, 1978), connections (Zeki, 1973;Seltzer and Pandya, 1978;Desimone et al, 1980), and receptive field size (Desimone and Gross, 1979), suggesting that there may be more than one functionally distinct subdivision of this region. Posterior parietal cortex (area 7, or PG and PE) occupies much of callosal recipient zone 6 (Lynch et al, 1977;Robinson et al, 1978).…”

Section: A Standard Representation Of Callosal Projectionsmentioning

confidence: 99%

The pattern of interhemispheric connections and its relationship to extrastriate visual areas in the macaque monkey

Essen¹,

Newsome²,

Bixby³

1982

J. Neurosci.

298

160

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The distribution of interhemispheric connections was studied in extrastriate visual cortex of the macaque monkey. Callosal fiber terminations were identified by staining for anterograde degeneration following transection of the splenium of the corpus callosum. Retrogradely labeled cell bodies of callosal projection neurons were identified histochemically following application of horseradish peroxidase to the cut surface of the callosum. Results were displayed on unfolded, two-dimensional representations of the cortex, which permitted spatial and topological relationships between callosal recipient and callosal free cortical regions to be discerned readily.The overall pattern of callosal inputs to visual cortex can be subdivided into nine callosal recipient zones which surround seven callosal free regions in the occipital, temporal, and parietal lobes. This pattern provides reliable and useful landmarks for identifying the borders of at least five topographically organized extrastriate visual areas. There is a pronounced dorsoventral asymmetry in callosal projections, not recognized in previous studies, which reflects an asymmetry in the organization of visual areas in dorsal versus ventral halves of the occipital lobe.The pattern of callosal fiber terminations is mirrored by a very similar distribution of callosal projection neurons. There are significant regional differences in the laminar distribution of callosal projection cells, and these differences may reflect functionally distinct cortical subdivisions.A considerable degree of individual variability was found in the relationship of callosal connections to gyral and sulcal landmarks as well as in the fine structure of individual callosal recipient strips, suggesting that each animal has a unique "callosal fingerprint." These findings emphasize the usefulness of the callosal pathway in elucidating the functional organization of extrastriate visual cortex.

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Comparison of the cortical degeneration in the visual regions of the temporal lobe of the monkey following section of the anterior commissure and the splenium

Cited by 89 publications

References 17 publications

Formation of mnemonic neuronal responses to visual paired associates in inferotemporal cortex is impaired by perirhinal and entorhinal lesions.

Formation of mnemonic neuronal responses to visual paired associates in inferotemporal cortex is impaired by perirhinal and entorhinal lesions.

Increased Axon Number in the Anterior Commissure of Mice Lacking a Corpus Callosum

The pattern of interhemispheric connections and its relationship to extrastriate visual areas in the macaque monkey

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