Synapses made by axons of callosal projection neurons in mouse somatosensory cortex: Emphasis on intrinsic connections

White, Edward L.; Czeiger, David

doi:10.1002/cne.903030206

Cited by 54 publications

(32 citation statements)

References 70 publications

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“…Young adult, male CD/1 mice were anesthetized with sodium pentobarbitol (80 mg/kg), and horseradish peroxidase (HRP) was applied to the cut ends of callosal axons as described in detail previously (White and Czeiger, 1991;Czeiger and White, 1993). Three days later, the mice were anesthetized deeply with chloral hydrate and perfused with a fixative containing 4% paraformaldehyde, 0.3% glutaraldehyde, and 15% of a saturated picric acid solution in 0.1 M phosphate buffer.…”

Section: Methodsmentioning

confidence: 99%

Comparison of the distribution of parvalbumin-immunoreactive and other synapses onto the somata of callosal projection neurons in mouse visual and somatosensory cortex

Czeiger

White

1997

J. Comp. Neurol.

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The distribution of synapses made by parvalbumin-immunoreactive (pv-ir) and nonimmunoreactive terminals was determined for the cell bodies of callosal projection neurons in the somatosensory and visual areas of mouse cerebral cortex. Callosal neurons were labeled by the retrograde transport of horseradish peroxidase applied to the contralateral hemisphere. The surface areas of somata belonging to callosal cells in somatosensory cortex ranged from 230 to 243 microm2 in size and received roughly one-third of their synapses from pv-ir terminals. Visual cortex, in contrast, contained two populations of callosal cell bodies: relatively large ones ranging in size from 255 to 279 microm2 that received 3-9% of their synapses from pv-ir terminals and smaller cell bodies that both in size (232-237 microm2) and in the proportion of synapses received from pv-ir terminals resemble the callosal cells examined in somatosensory cortex. That different functional areas of the cortex have populations of callosal cells similar in size, and displaying similar patterns of somatic synapses, supports the notion that a common plan of synaptic connectivity characterizes different functional areas. Results in visual cortex indicate that functional areas contain, in addition, area-specific patterns of synapses.

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Section: Methodsmentioning

confidence: 99%

Comparison of the distribution of parvalbumin-immunoreactive and other synapses onto the somata of callosal projection neurons in mouse visual and somatosensory cortex

Czeiger

White

1997

J. Comp. Neurol.

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“…However, other data suggest that this phenomenon might be limited to high-order cortical areas. In the primary visual (Kisvárday et al, 1986;Gabbott et al, 1987;McGuire et al, 1991), somatosensory (Elhanany and White, 1990;White and Czeiger, 1991), and motor cortices (Keller and Asanuma, 1993), a lower proportion of elements postsynaptic to intrinsic axons contributed by pyramidal neurons are dendritic spines (ϳ75-90%), with no difference between proximal and distal projections.…”

Section: The Responses Of Perirhinal Cells To Neocortical Stimuli Depmentioning

confidence: 99%

Propagation of Neocortical Inputs in the Perirhinal Cortex

2001

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The perirhinal area is a rostrocaudally oriented strip of cortex in which lesions produce memory and perceptual impairments. It receives topographically organized transverse projections from associative neocortical areas and is endowed with intrinsic longitudinal connections that could distribute neocortical inputs in the rostrocaudal axis. In search of distinguishing network properties that might support perirhinal involvement in memory, we have performed whole-cell recordings in horizontal perirhinal slices with preserved transverse neocortical links and intrinsic longitudinal connections. Neocortical stimulation sites in rostrocaudal register with regular spiking perirhinal neurons elicited a sequence of excitatory and inhibitory synaptic potentials. In contrast, apparently pure excitatory responses were observed when the stimulating and recording sites were separated by Ն1 mm in the rostrocaudal axis. This suggested that adjacent and distant neocortical stimuli influence regular spiking perirhinal neurons by pathways that respectively form and do not form synapses with inhibitory interneurons. In keeping with this, presumed interneurons did not respond to distant neocortical stimuli. These results suggest that neocortical inputs recruit perirhinal inhibitory interneurons located at the same transverse level, limiting the depolarization of principal perirhinal cells. In contrast, distant neocortical inputs only evoke excitation because longitudinal perirhinal pathways do not engage inhibitory interneurons. This leads us to suggest that the perirhinal network is biased to favor Hebbian-like associative interactions between coincident and spatially distributed inputs. Key words: perirhinal; neocortex; inhibition; horizontal connections; learning; memoryIn the fundus and lateral bank of the rhinal fissure are cortical areas collectively known as the perirhinal cortex. These areas are believed to play a critical role in high-order perceptual and mnemonic functions, because perirhinal lesions interfere with recognition and associative memory in various sensory modalities (Zola-Morgan et al

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“…For example, 97% of the intrinsic axon collaterals of callosally projecting pyramidal neurons in mouse visual cortex were reported to contact dendritic spines (Czeiger and White, 1993). Moreover, other investigations (Elhanany and White, 1990;White and Czeiger, 1991) in mouse somatosensory cortex have revealed that approximately 90% of intrinsic axon collaterals of both associational and callosal pyramidal neurons synapse onto dendritic spines. In contrast, the percentage of intrinsic axon projections forming excitatory synapses with dendritic spines appears to be substantially lower in other cortical systems.…”

Section: Target Specificity Of Supragranular Pyramidal Neuron Projectmentioning

confidence: 99%

Synaptic targets of pyramidal neurons providing intrinsic horizontal connections in monkey prefrontal cortex

et al. 1998

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xũ I sLxxJ In monkey prefrontal cortex, the intrinsic axon collaterals of supragranular pyramidal neurons extend horizontally for considerable distances through the gray matter and give rise to stripe-like clusters of axon terminals (Levitt et al. [1993] J. Comp. Neurol. 338:360-376). Because understanding the functional role of these connections requires knowledge of their synaptic targets, we made injections of biotinylated dextran amine (BDA) into layer 3 of macaque prefrontal area 9 and examined the labeled intrinsic axon collaterals by electron microscopy. Labeled axon terminals formed exclusively asymmetric synapses, and 95.6% of the postsynaptic structures were dendritic spines, presumably belonging to other pyramidal neurons. The remaining postsynaptic structures were dendritic shafts, many of which had the morphological characteristics of local circuit neurons. The prefrontal injections also labeled associational projections that traveled through the white matter to terminate in other areas of prefrontal cortex. All of the synapses formed by these associational axons were asymmetric, and 91.9% were onto dendritic spines. The similarities in synaptic targets of the prefrontal intrinsic and associational axon terminals suggested that these projections might arise from the same neurons, an interpretation confirmed in dual label, retrograde tracing studies. To determine the specificity of the synaptic targets of these prefrontal connections, two additional comparisons were made. In the posterior parietal cortex (area 7a), 94.2% of the synapses furnished by BDA-labeled intrinsic collaterals of supragranular pyramidal neurons were also with dendritic spines. In contrast, only 75.6% of unlabeled asymmetric synapses in the prefrontal cortex were onto dendritic spines. These comparisons suggest that the axons of supragranular pyramidal neurons in primate association cortices are preferentially directed to specific targets. Finally, after injections of BDA, a small number of retrogradely labeled pyramidal neurons were observed within the anterogradely labeled clusters of intrinsic axon terminals. At the ultrastructural level, synapses between anterogradely labeled axon terminals and retrogradely labeled dendritic spines were identified. These findings suggest that reciprocal, monosynaptic connections may exist between pyramidal neurons located in different stripe-like clusters, providing a potential anatomical substrate for reverberating excitatory circuits within the primate association cortices.

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Synapses made by axons of callosal projection neurons in mouse somatosensory cortex: Emphasis on intrinsic connections

Cited by 54 publications

References 70 publications

Comparison of the distribution of parvalbumin-immunoreactive and other synapses onto the somata of callosal projection neurons in mouse visual and somatosensory cortex

Comparison of the distribution of parvalbumin-immunoreactive and other synapses onto the somata of callosal projection neurons in mouse visual and somatosensory cortex

Propagation of Neocortical Inputs in the Perirhinal Cortex

Synaptic targets of pyramidal neurons providing intrinsic horizontal connections in monkey prefrontal cortex

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