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PubMed1988

The corpus callosum is larger with right-hemisphere cerebral speech dominance.

Variations in the size of the human corpus callosum were examined as a possible morphological substrate of functional asymmetries of the cerebral hemispheres, such as cerebral speech dominance. The midsagittal surface area of the corpus callosum, obtained by magnetic resonance imaging, was measured in 50 patients with epilepsy and 50 neurologically normal control subjects. The mean callosal area did not differ significantly between patients and control subjects, between left-handed and right-handed subjects, or between men and women. When measurements were compared among 44 patients, whose cerebral speech dominance had been determined by the intracarotid injection of sodium amytal, the area of the corpus callosum was significantly greater in patients with right-hemisphere cerebral speech dominance. The mean callosal area was greater by 109 to 159 square millimeters (18-28%) when compared to that of patients with either left-hemisphere speech dominance or bilateral speech representation. This difference in midsagittal surface area could represent as many as 37 to 54 million additional callosal axons in subjects with right-hemisphere cerebral speech dominance.

Adolescent↗
PubMed2003

Single-cell study of motor cortex projections to the barrel field in rats.

In freely moving rats, whisking is associated with a slow modulation of neuronal excitability in the primary somatosensory cortex. Because it persists after the blockade of vibrissa input, it was suggested that the slow modulation might be mediated by motor-sensory corticocortical connections and perhaps result from the corollary discharges of corticofugal cells. In the present study, we identified motor cortical cells that project to the barrel field and reconstructed their axonal projections after juxtacellularly staining single cells with a biotinylated tracer. On the basis of the final destination of main axons, two groups of neurons contribute to motor-sensory projections: callosal cells (87.5%) and corticofugal cells (12.5%). Axon collaterals of callosal cells arborize in layers five to six of the granular and dysgranular zones and give off several branches that ascend between the barrels to ramify in the molecular layer. In contrast, the axon collaterals of corticofugal cells do not ramify in the infragranular layers but in layer 1. The origin of the majority of motor sensory projections from callosally projecting cells does not support the notion that the slow modulation results from the corollary discharges of corticofugal axons. It would rather originate from a separate population of cells, which could output the slow signal to the barrel field in parallel with the corticofugal commands to a brainstem pattern generator. As free whisking is characterized by bilateral concerted movements of the vibrissae, the transcallosal contribution of motor-sensory axons represents a substrate for synchronizing the slow modulation across both hemispheres.

Animals↗
PubMed1978

Organization of corticocortical connections in the parietal cortex of the rat.

An analysis based on Nissl, anterograde degeneration, and succinic dehydrogenase histochemical techniques reveals that there are two distinct regions of parietal cortex which are characterized by different cytoarchitectonic features and anatomical connections. The "granular" cortical zone possesses a well-defined fourth layer composed of small, densely-packed cells, receives dense projections from the ventral posterior nucleus of the thalamus, and is essentially free of callosal inputs. "Agranular" cortical areas which surround or lie embedded within the granular zone lack a well-defined fourth layer, receive sparse projection from the ventral posterior nucleus, but send and receive extensive callosal projections. These findings suggest that thalamic and callosal projections to the parietal cortex maintain a pattern of areal segregation. The granular cortical zone, which apparently corresponds to SmI, projects ipsilaterally to motor cortex, SmII, and adjacent agranular areas. The superficial layers of the granular cortex also project heavily upon the underlying layer V. This intracortical projection is not organized in discrete clusters within the "barrel field" cortex. This suggests that the specialized organization of thalamic afferents and granule cells within the "barrel field" is not maintained in the intracortical circuitry of this region.

Animals↗
PubMed1981

Efferent systems of the rabbit visual cortex: laminar distribution of the cells of origin, axonal conduction velocities, and identification of axonal branches.

Several efferent systems of visual area I in Dutch rabbits were studied with anatomical (horseradish peroxidase) and physiological (antidromic) methods. Anatomical studies provided information regarding the laminar origin of the projections to the contralateral hemisphere, visual area II, the dorsal lateral geniculate nucleus, and the superior colliculus. Physiological studies provided information regarding conduction velocities and multiple destinations of efferent axons. Both the callosal projection and the projection to V-II were shown to originate primarily in layer II-III. However, approximately 10-20% of the callosal projection and 20-40% of the projection to V-II originated in layers IV and V. In contrast, the projection to the dorsal lateral geniculate nucleus originated nearly exclusively in layer VI, while corticotectal neurons occurred primarily in layer V. A significant number of corticotectal neurons were, however, found in layer IV. Thus, the above efferent systems were found to differ in their principal laminar origin and in the diffuseness of that origin. The origins of corticocortical projections were considerably more diffuse than those of corticofugal projections. In addition to differences in laminar origin, efferent systems also differed significantly in the conduction velocities of their axons. The projection to visual area II and to the lateral geniculate nucleus consisted primarily of very slowly conducting axons, while the projection to the superior colliculus was fast conduction. The callosal projection consisted of both slow and fact conduction axons. Finally, the question of branching of V-I efferent axons was addressed. Although the laminar origin of the projections to the contralateral hemisphere and to visual area II overlapped considerably, none of these corticocortical axons could be shown to project to both locations or to a subcortical destination. In contrast, approximately one-third of corticotectal axons were shown to project a collateral into the thalamus. Although the destination of this collateral is unclear, it is medial to the lateral geniculate nucleus and may be the pulvinar.

Animals↗
PubMed1986

The lamination and connectivity of embryonic cerebral cortex transplanted into newborn rat cortex.

Sheets of frontal or occipital cerebral cortex were taken from embryonic day (E) 15 rat embryos and placed in shallow depressions made in the occipitoparietal region of newborn rats. These transplants developed normal patterns of lamination, which could be in an inverted orientation if the transplant itself was placed upside down. Irrespective of the cortical area of origin of the grafted tissue, the transplants consistently received projections from those host thalamic nuclei that were normally found to innervate the adjacent host cortex. This indicates that immature cortical tissue, up to at least E15, may not contain the information necessary to define the specific thalamocortical connections characteristic of individual areas. On the contrary, the observed input pattern may be the result of sprouting of fibers that normally innervated host cortical regions adjacent to the transplant. Similarly, callosal afferents to transplants seemed to be a direct extension of the callosal input to the host cortex immediately beneath the transplant. Results from HRP studies of callosal connections indicated that transplant efferents to the contralateral cortex are smaller in magnitude than their afferents. This may be related to the superficial location of the transplants, which may limit the access transplant efferents have to the white matter. This study suggests that, while the cortical lamination is largely determined intrinsically, the innervation of the cortex is influenced by the context in which it develops.

Animals↗
PubMed1987

Cingulate cortex of the rhesus monkey: I. Cytoarchitecture and thalamic afferents.

The cytoarchitecture and thalamic afferents of cingulate cortex were evaluated in the rhesus monkey (Macaca mulatta). Area 24 has three divisions of which area 24a is adjacent to the callosal sulcus and has the least laminar differentiation. Area 24b has more clearly defined layers II, III, and Va, and area 24c, which forms the lower bank of the anterior cingulate sulcus, has a particularly dense layer III. Area 23 also has three divisions, each of which has a distinct layer IV. Area 23a is adjacent to the callosal sulcus and has the thinnest layers II-IV, which have the same cell density as layers V and VI. Area 23b has the largest pyramids in layers IIIc and Va, and area 23c, in the depths of the posterior cingulate sulcus, has the broadest external and thinnest internal pyramidal layers. Finally, areas 29 and 30 are located in the posterior depths of the callosal sulcus. Two divisions of area 29 are apparent: one with a granular layer directly adjacent to layer I (area 29a-c) and another with differentiation of layers III and IV (area 29d). Area 30 has a dysgranular layer IV. Injections of the retrograde tracer horseradish peroxidase (HRP) were made into subdivisions of cingulate cortex in the monkey. Area 25 received thalamic input mainly from the midline parataenial (Pt), central densocellular (Cdc), and reuniens nuclei as well as from the dorsal parvicellular division of the mediodorsal nucleus (MDpc). A less dense projection also originated in the intralaminar parafascicular (Pf), central superior, and limitans (Li) nuclei as well as the medial division of the anterior nuclei (AM). Areas 24a and 24b received most thalamic afferents from fusiform and multipolar cells in the Cdc and Pf nuclei with fewer from the ventral anterior (VA) and MDpc and MD densocellular (MDdc) nuclei and only minor input from AM. Most input to premotor cingulate area 24c appeared to originate in VA, MDdc, and Li. Area 29 received the most dense input from nuclei traditionally associated with limbic cortex including the anteroventral (AV), anterodorsal (AD), and laterodorsal (LD) nuclei. Areas 23a and 23b, in contrast, did not receive AV, AD, or LD input, but the greatest proportion of their thalamic afferents arose in AM. Less-pronounced input also came from the lateroposterior (LP), medial pulvinar, and MDdc nuclei.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed1988

Cortical connections of electrophysiologically and architectonically defined subdivisions of auditory cortex in squirrels.

Multiunit recordings with microelectrodes were used to identify and delimit subdivision of auditory cortex in squirrels. In the same animals, cortical connections of subdivisions of auditory cortex were determined by placing injections of the tracer wheat germ agglutinin conjugated with horseradish peroxidase (WGA-HRP) into electrophysiologically defined locations. The electrophysiological results and patterns of connections were later related to myeloarchitectonic distinctions in brain sections cut parallel to the surface of the artificially flattened cortex. As previously described (Merzenich et al.: J. Comp. Neurol. 166:387-402, '76), a primary auditory field, A-I, was characterized by (1) neurons narrowly tuned to tone frequency; (2) a tonotopic map with high frequencies, which represented caudal to low frequencies; and (3) dense myelination. A-I was reciprocally connected with a rostral field, R, a parietal ventral somatosensory representation, PV, cortex ventral to A-I, and other nearby regions of cortex of the same hemisphere. Callosal connections of A-I were with A-I, R, and two or more other regions of temporal cortex. The less densely myelinated rostral field, R, also had neurons that were frequency tuned, but the neurons were often less securely driven. R appeared to have a tonotopic organization that roughly mirrored that of A-I. Ipsilateral connections of R included A-I, PV, and cortex ventral and caudal to R. Callosal connections were with R, A-I, PV, and cortex ventral and caudal to R. Callosal connections were with R, A-I, PV, and other locations in temporal cortex. Cortex in caudal PV, ventral to A-I, and ventral to R was responsive to auditory stimuli, but responses to pure tones were weak and inconsistent, and habituation to a repeated stimulus was rapid. The cortex responsive to auditory stimuli included some but not all of the cortex connected with A-I and R. The results lead to the conclusion that auditory cortex of squirrels contains at least two tonotopically organized fields, possibly as many as five or more auditory fields, and at least two auditory-somatosensory fields.

Animals↗
PubMed1988

Death of the subcallosal glial sling is correlated with formation of the cavum septi pellucidi.

In this study we have examined the developmental fate of a population of cells that is located beneath the rostral corpus callosum during the perinatal period. These cells form a distinct slinglike structure along the geographically defined corticoseptal boundary (CSB) and may play a role in guiding callosal axons across the midline. The sling is a transient structure present in fetal and neonatal animals but not in adults. Here we show that the CSB cells die and that this debris is removed by macrophages. The sequence of cell degeneration in the CSB is highly stereotyped and follows a spatiotemporal pattern that is correlated with fusion of the cerebral hemispheres and subsequent growth across the midline of the callosal axons. The subcallosal location of the resorbing CSB is found in the exact place in which a fluid-filled cavity (the cavum septi pellucidi) is transiently found during the perinatal period. The tight temporal and spatial correlation between callosal axon decussation, degeneration of the CSB, and cavum septi formation suggests that these three phenomena may be causally related.

Aging↗
PubMed1989

Cortical connections of areas 17 (V-I) and 18 (V-II) of squirrels.

Connections of visual cortex in squirrels were investigated by placing WGA-HRP injections, and in some cases fluorescent dyes, into area 17 (V-I) or area 18 (V-II). Results were related to architectonic fields determined in brain sections cut parallel to the surface of manually flattened cortex and to limited microelectrode mapping data. Injections in area 17 provided evidence for 1) a patchy pattern of horizontal intrinsic connections extending 1-2 mm from the injection site; 2) uneven, widely distributed connections with area 18 (V-II) and adjoining occipital-temporal (OT) cortex; and 3) callosal connections of large portions of area 17 with the 17/18 border zone. While restricted locations in area 17 had uneven interconnections over several mm of area 18, more rostral locations in area 17 related to more rostral locations in area 18, demonstrating a topographic tendency. Injections in area 18 revealed 1) zones of discontinuous connections with area 17 that followed a topographic pattern, 2) patches of intrinsic connections that spread over distances of up to 6-8 mm from the injection site; 3) two zones of uneven connections with OT cortex suggesting the locations of at least two visual areas, OTr and OTc; 4) connections with limbic cortex rostromedial to areas 17 and 18; 5) sparse connections with regions of temporal cortex lateral to OT; and 6) uneven callosal connections with area 18 and OT cortex. The widespread and unevenly distributed intrinsic callosal interconnection patterns of areas 17 and 18 contrast with the restricted excitatory receptive fields of neurons and the retinotopic patterns of representation in these fields. Although physiological evidence is presently lacking, the patchy connections suggest that areas 17 and 18 in squirrels are modularly organized.

Animals↗
PubMed1991

Patterns of synaptic input on corticocortical and corticothalamic cells in the cat visual cortex. II. The axon initial segment.

In the present study we examined the synaptology of the axon initial segments (AISs) of three populations of retrogradely labeled pyramidal cells: callosal, corticothalamic, and ipsilateral corticocortical projecting cells. The cells were labeled by horseradish peroxidase injected into the contralateral visual cortex, the ipsilateral lateral geniculate nucleus, or area 19 of the ipsilateral hemisphere. The AISs of these cells were completely reconstructed from tracings of serial electron micrographs and the number and type of synapses ending on them determined. These data were compared with that described in the companion paper (Fariñas and DeFelipe, J Comp Neurol 1991; 304:53-69), in which the ultrastructure and synaptology of the somata of callosal and corticothalamic cells was investigated. Together, these data permit comparisons to be made between the somatic and axonic innervation of the same cells. Our results show that each population of efferent cells examined received a characteristic and rather homogeneous number (in comparison with the number of axosomatic synapses) of axoaxonic synapses: 16 to 23 for AISs of callosal cells, 22 to 28 for ipsilateral corticocortical cells, and 1 to 5 for corticothalamic cells. Since most axoaxonic synapses are likely to be GABAergic, it is concluded that each population of pyramidal cells receives a distinct GABAergic inhibitory synaptic profile.

Animals↗
PubMed1992

Somatosensory receptive field properties of corpus callosum fibres in the raccoon.

Anatomical studies in a number of species have shown that most areas of the somatosensory cortex are callosally interconnected. This is also true for the raccoon, at least for those parts representing proximal and axial body regions. Electrophysiologically, studies carried out in cats and monkeys have demonstrated that all sensory sub-modalities cross in the callosum. Moreover, cells representing the paws and fingers, though occupying a large portion of areas SI and SII, seem to send proportionately fewer axons through the callosum than axial structures. No comparable study has been carried out in the raccoon. The purpose of the present experiment was therefore to investigate the functional organization of the callosal system in this animal by examining the receptive field properties of the somatosensory fibres crossing in the callosum. Axonal activity was recorded directly through tungsten microelectrodes in the corpus callosum of eight raccoons. Results indicated that somatosensory information is transmitted in its rostral portion. Most receptive fields concerned axial and proximal body regions and the head and face. Some receptive fields represented para-axial regions of the body and a few concerned the hands and fingers. Slowly and rapidly adapting fibres were found, as were all the sensory sub-modalities tested. A substantial proportion of the axons had bilateral receptive fields. These results are discussed in relation to those obtained in other species, with particular reference to: (1) the midline fusion hypothesis of callosal function; (2) the representation within this structure of the distal extremities, and (3) the origin of the bilateral receptive fields.

Animals↗
PubMed1994

Postnatal development of parvalbumin immunoreactivity in the cerebral cortex of the cat.

Parvalbumin immunoreactivity in the developing neocortex of the cat progresses following specific laminar, areal, and, in a particular area, roughly anteroposterior gradients. Parvalbumin immunoreactivity first occurs in basket cells and later in chandelier neurons. Pyramid-like immunoreactive neurons are also transitorily observed from the second to the third week in layer V of the auditory association-related areas. Parvalbumin-immunoreactive neurons first appear in the primary somatosensory cortex and primary auditory and visual areas, followed by the primary motor and polysensory association areas and, finally, the auditory association areas and cortical areas related to the limbic system. In addition to cortical neurons, three fiber systems are immunolabeled with antiparvalbumin antibodies: thalamocortical, callosal, and ipsilateral corticocortical. Parvalbumin-immunoreactive thalamocortical fibers appear during the first month of postnatal life. Parvalbumin-immunoreactive callosal and ipsilateral corticocortical fibers are seen from the fourth postnatal week onward. Because all parvalbumin-immunoreactive cortical neurons in adulthood are nonpyramidal inhibitory cells, the present findings suggest that a number of ipsilateral corticocortical and callosal connections may be inhibitory.

Aging↗
PubMed2002

Corpus callosum shape and neuropsychological deficits in adult males with heavy fetal alcohol exposure.

Persons with brain damage consequent to prenatal alcohol exposure have typically been diagnosed with either fetal alcohol syndrome (FAS) or fetal alcohol effects (FAE), depending on facial features. There is great variability of behavioral deficits within these groups. We sought to combine neuroanatomical measures with neurocognitive and neuromotor measures in criteria of greater sensitivity over the variety of consequences of alcohol exposure. To this end, midline curves of the corpus callosum were carefully digitized in three dimensions from T1-weighted MR scans of 15 adult males diagnosed with FAS, 15 with FAE, and 15 who were unexposed and clinically normal. From 5 h of neuropsychological testing we extracted 260 scores and ratings pertaining to attention, memory, executive function, fine and gross motor performance, and intelligence. Callosal midline shape was analyzed by new morphometric methods, and the relation of shape to behavior by partial least squares. The FAS and FAE subgroups have strikingly more variability of callosal shape than our normal subjects. With the excess shape variation are associated two different profiles of behavioral deficit unrelated to full-scale IQ or to the FAS/FAE distinction within the exposed subgroup. A relatively thick callosum is associated with a pattern of deficit in executive function; one that is relatively thin, with a deficit in motor function. The two combine in a very promising bipolar discrimination of the exposed from the unexposed in this sample. Thus there is considerable information in callosal form for prognosis of neuropsychological deficits in this frequently encountered birth defect.

Adolescent↗
PubMed2002

White matter glucose metabolism during intracortical electrostimulation: a quantitative [(18)F]Fluorodeoxyglucose autoradiography study in the rat.

[(18)F]Fluorodeoxyglucose (FDG) autoradiography was used to analyze the effects of intracortical electrostimulation on local cerebral metabolic rate for glucose (LCMRglu). The hindleg area in rat brains was electrically stimulated with different frequencies (0, 0.1, 0.25, 0.5, 0.75, 1 stimulus trains per second, two animals per condition). The major result was a strong positive correlation between stimulation frequency and LCMRglu in the callosal fibers originating in the stimulated cortical area. At the highest stimulation frequency callosal LCMRglu was 50.01 micromol/min/100 g compared to 27.87 micromol/min/100 g at baseline. LCMRglu in gray and white matter control areas was stable across conditions. Direct injection of FDG in the stimulated cortex failed to produce increased callosal uptake, excluding the possibility that FDG uptake in the corpus callosum is related to axonal diffusion. Although several previous autoradiographic studies have demonstrated alterations in LCMRglu in white matter, correlations between neural activity and LCMRglu have never been explicitly addressed. Changes in white matter metabolism most likely reflect changes of electrical fiber activity and thus the presented results bear important implications for brain imaging studies.

Animals↗
PubMed1998

Corpus callosum in Alzheimer's disease and vascular dementia--a quantitative magnetic resonance study.

We investigated atrophic alterations in different regions of the corpus callosum in Alzheimer's disease (AD) and vascular dementia (VD) with respect to clinical changes. 32 patients with AD (NINCDS-ADRDA criteria), 17 patients with VD (NINDS-AIREN criteria) and 13 healthy control subjects were included. 3-D MRI sequences were acquired using a 1.5T MRI scanner. The size of the corpus callosum and its subdivisions was sampled on 5 mid-saggital slices using a personal computer-based software. Total callosal size was significantly reduced in AD but not in VD. Furthermore, the most rostral parts of the corpus callosum were significantly smaller in AD when compared to controls. Again, these changes were not found in patients with VD. Severity of dementia was significantly correlated with the size of the midbody of the corpus callosum in AD. Callosal atrophy in AD may reflect the severity and pattern of cortical neuronal damage occurring mostly in the inferior frontal, anterior parietal and midtemporal regions. Correlations between regional callosal atrophy and severity of dementia indicate that interhemispheric cortico-cortical disconnections may contribute to the dementia syndrome.

Aged↗
PubMed1990

Comparative study of visual inter and intrahemispheric cortico-cortical connections in five native Chilean rodents.

Previous studies of the visual cortical organization in the rat and other rodent species have raised the possibility that the visual cortical plan in the rat is common to a large number of species within the order. We have tested this idea by comparing the visual plan in the rat to cortical subdivision schemes obtained from five native Chilean rodent species, including members of the Cricetidae family within the Miomorph group, as well as from the Octodontidae family within the Caviomorph group. Cortical subdivision schemes were inferred from the analysis of the patterns of callosal connections revealed following multiple injections of HRP contralaterally, as well as from ipsilateral cortico-cortical connections observed after small injections of horseradish peroxidase conjugated with wheat germ agglutinin (WGA-HRP) into striate cortex. As in the rat, callosal connections in the native rodents concentrate at the border between cytoarchitectonic areas 17 and 18a, and along the borders of discrete, sparsely callosal islands of cortex in lateral peristriate cortex. Furthermore, single injections of WGA-HRP into striate cortex produce multiple, separate fields of labeled cells and terminations in the cortex surrounding area 17. Together, our data supports the idea of a common plan of visual cortical organization among rodents by providing evidence that the visual cortex in the native species is subdivided into multiple visual areas in a manner that resembles the rat cortical plan.

Animals↗
PubMed1978

Characteristics of interhemispheric impulse conduction between prelunate gyri of the rhesus monkey.

Cells of origin of the corpus callosum (callosal efferent neurons) in prelunate gyrus (area OA) of the rhesus monkey were studied using electrophysiological techniques. Monkeys were chronically prepared and callosal efferent neurons were identified by their antidromic activation following electrical stimulation of the contralateral prelunate gyrus and/or the splenium of the corpus callosum. Interhemispheric antidromic latencies ranged from 2.6--18.0 ms (median = 7.0 ms) while the conduction velocity along the length of the axon ranged from 2.8 to 22.5 M/s (median = 7.4 M/s) while the conduction velocity along the length of the axon ranged from 2.8 to 22.5 M/s (median = 7.4 M/s. Following the relative refractory period of a single prior impulse, all but one of 61 callosal efferent neurons studied showed a supernormal period of increased axonal conduction velocity and excitability. Following several prior impulses, the supernormal period was followed by a subnormal period of decreased axonal conduction velocity and excitability, which, depending on the number of prior impulses, lasted from several hundred ms to nearly 2 min.

Animals↗
PubMed1982

Visual receptive field properties of cells innervated through the corpus callosum in the cat.

The present experiment examined the receptive field (R.F.) properties of cortical cells which receive part of their input from the contralateral hemisphere via the corpus callosum. Two groups of cats were used to recording unit activity: a normal control group, and an experimental group consisting of cats which had their optic chiasmas split across the midline prior to the recording sessions. Acute recordings were carried out in the conventional manner using tungsten microelectrodes and N2O: O2 anaesthesia. The recording site was the 17-18 border. The stimulus consisted of a thin bar generated on an oscilloscope screen by a computer. The bar, whose orientation was varied automatically from 0 degrees to 345 degrees in 15 degrees steps, was swept across the screen at constant speed orthogonal to the orientation. Various R.F. properties were studied using both quantitative and qualitative criteria. Thus, in the normal cat, simple, complex and hypercomplex type R.F.'s were found, whereas no callosally activated cell was of the simple type. The ocular dominance distribution found in the split chiasma cat was skewed towards the ipsilateral eye, although a fairly large number of cells could be driven with the two eyes. The R.F.'s of the callosally activated neurons were all situated close to the vertical neurons were all situated close to the vertical meridian, which they sometimes straddled. Both in the normal and in the chiasma sectioned cats, the complex cells had larger R.F.'s than the other cell types. However, the R.F.'s determined through the ipsilateral eye was essentially of the same dimensions as those obtained through the indirect interhemispheric pathway, and this irrespective of cell type. Orientation specificity was similar for the two eyes in the split chiasma cats as it was for the normal cats although in the former the orientation tuning curve was narrower for the callosal pathway than for the more direct thalamo-cortical pathway. The results are interpreted within the context of the different functions ascribed to the corpus callosum in vision.

Animals↗