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T Tsumoto

Publications and source records attributed to T Tsumoto.

At least 91 records · Page 5Linked to original sources
PubMed1987

A functional role of cholinergic innervation to neurons in the cat visual cortex.

1. Effects of microionophoretic application of acetylcholine (ACh) and its antagonists on neuronal responses to visual stimuli and to electrical stimulation of the lateral geniculate nucleus were studied in the cat striate cortex. 2. Responses elicited visually and electrically were facilitated by ACh in 74% of the cells tested, whereas the responses were suppressed in 16%. These ACh effects were blocked by a muscarinic antagonist, atropine, but not by a nicotinic antagonist, hexamethonium, indicating that the ACh effects are mediated through muscarinic receptors. A single application of atropine suppressed visual responses of cells facilitated by ACh, whereas it enhanced those of cells inhibited by ACh, suggesting that endogenous ACh may tonically modulate visual responsivity of cortical neurons. 3. In most cells with the facilitatory ACh effect, responses with single spikes to the electrical stimulation became more consistent, often with double spikes, during the ACh application. The suppressive effects of ACh were noted most often in cells with a longer response latency to electrical stimulation of lateral geniculate nucleus. 4. In most of the facilitated cells the spontaneous activity remained null or very low during ACh application, in spite of marked enhancement of visual responses, suggesting that ACh may improve the signal-to-noise ratio (S/N) of cortical neuron activity. To confirm this suggestion, we calculated a S/S + N index by counting the total number of spikes in the responses (S) and that in peristimulus time histogram (S + N) and found that it was improved during the ACh application in about a half of the cells, whereas it became worse in about one-fifth. 5. In most of the facilitated cells, ACh enhanced visual responses not only to optimal but also to nonoptimal stimuli, resulting in no improvement or even worsening of the orientation selectivity. This was also the case in the selectivity of direction of stimulus movement. 6. The laminar location of the facilitated cells was biased toward layers V and VI of the cortex, although they also made up the majority in layers II + III and about half the tested cells in layers IVab and IVc. 7. In the light of recent understanding of cortical circuitry, these results suggest that the cholinergic innervation to cortical neurons may play a role in improvement of the S/N ratio of information processing in the striate cortex and in facilitation of sending processed informations to other visual centers.

Acetylcholine↗
PubMed1987

Effects of cholinergic depletion on neuron activities in the cat visual cortex.

1. Unilateral lesions of the nucleus basalis magnocellularis (nBM), a source of cholinergic projection to the cerebral cortex, were produced by injection of kainic acid in the cat. The lesions caused a significant reduction in density of choline acetyltransferase-immunoreactive terminals in the visual cortex ipsilateral to the lesions. 2. In the primary visual cortex ipsilateral to the lesions [acetylcholine (ACh)-depleted cortex], about half of the cells had weak or undetectable visual responses, whereas in the contralateral visual cortex almost all the cells had normal responsivity. The response selectivity, such as orientation and direction selectivities, of cortical cells was not affected by the depletion of ACh. 3. The microionophoretic application of ACh to cells under observation facilitated visual responses in 83% of the cells recorded from the ACh-depleted cortex, whereas it suppressed the responses in only 9%. The application of a muscarinic antagonist, atropine, to cells in the ACh-depleted cortex was ineffective, suggesting no residual ACh activity. 4. The mean current required to induce facilitation in the cortex ipsilateral to the lesion was significantly smaller than that required in the contralateral cortex and the visual cortex of the normal cat, suggesting a supersensitivity of receptors mediating the effect or a reduction in catabolism of exogenous ACh in the ACh-depleted cortex. 5. More than half of the cells that had been unresponsive to visual stimuli became clearly responsive during the ACh application. The response magnitude of cortical cells, as a whole, increased to the same degree as that observed during the ACh application in the normal cat. 6. In addition to the decrease in the average response magnitude, there was a remarkable variability in responses of cells to motion of the slit from sweep to sweep in the ACh-depleted cortex. The application of ACh to cortical cells decreased the variability of responses and consequently made the responses much more consistent. 7. These results suggest that without ACh supplied from the nBM, most of the cortical neurons could not respond briskly and consistently to excitatory inputs and that exogenously applied ACh could reverse such an impairment of cortical neurons through intact or even supersensitive postsynaptic receptors.

Acetylcholine↗
PubMed1986

Excitatory amino acid transmitters in neuronal circuits of the cat visual cortex.

To test a possibility that glutamate (Glu) and aspartate (Asp) are transmitters in the visual cortex and to locate their operating sites in the cortical circuitry, we studied effects of microiontophoretic application of Glu/Asp antagonists on visual responses of cortical neurons in the cat. The antagonists tested were kynurenic acid (KYNA), cis-2,3-piperidine dicarboxylic acid, and gamma-D-glutamylglycine. Among these antagonists, KYNA was most effective in blocking visual responses of cortical neurons; it eliminated visual responses in 156 of the 188 cells tested. Usually the maximal suppressive effect appeared 20-30 s after starting KYNA application and recovery of cell's responsiveness 30-60 s after stopping the application. KYNA antagonized excitations induced by ionophoretic application of Glu and Asp but did not block those by acetylcholine, suggesting that KYNA is a selective antagonist of Glu/Asp, and its action is not due to general depressant effects. This suggestion was further supported by the observation that in corticogeniculate cells the latency and probability of invasion of antidromic spikes into the somatodendritic part following electrical stimulation of the lateral geniculate were not changed while visual responses were completely suppressed by KYNA. In terms of actions of the three agonists which give the basis for classifying excitatory amino acid receptors into at least three types, KYNA antagonized excitations by N-methyl-D-aspartic acid (NMDA) and kainate in almost all the cells tested but did not block those by quisqualate in about half of the cells. These results suggest that KYNA reacts more preferentially with NMDA and kainate receptors than with quisqualate receptors. Effectiveness of KYNA was related to types of receptive fields of cells and to their laminar locations. In 79 of the 104 simple cells tested, KYNA completely suppressed their visual responses, while such a complete block was seen in only 18 of the 68 complex and 3 of the 16 special complex cells. The great majority of the cells in layers IVab, IVc and the upper part of layer VI were completely suppressed by KYNA, whereas most of the cells in the other layers were incompletely suppressed or not suppressed at all.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetylcholine↗
PubMed1985

GABAergic inhibition and orientation selectivity of neurons in the kitten visual cortex at the time of eye opening.

Effects of iontophoretic application of gamma-aminobutyric acid (GABA) and its antagonist, N-methyl-bicuculline (BIC), on visual responses of striate cortical neurons were studied in kittens 6-13 days old. Visually responsive cells were classified into three groups, i.e. orientation-selective, orientation-bias and nonoriented cells. In almost all of the orientation-selective cells, their responses were completely suppressed by GABA while the majority of the others were not significantly or only weakly suppressed. An application of BIC abolished or reduced the selectivity of all the orientation-selective cells but did not affect any of the nonoriented cells tested. These results suggest that GABAergic inhibition already operates on a group of cortical neurons to make them orientation-selective at the time of eye opening, but such an action of GABA on other groups of neurons develops later.

Animals↗
PubMed1984

GABAergic inhibition already operates on a group of neurons in the kitten visual cortex at the time of eye opening.

Effects of iontophoretic application of gamma-aminobutyric acid (GABA) and its antagonist, N-methyl-bicuculline (BIC), on visual responses of striate cortical neurons were studied in kittens 6-13 days old. Visually responsive cells were classified into 3 groups, i.e., orientation-selective, orientational bias and non-oriented cells. In almost all of the orientation-selective cells their responses were completely suppressed by GABA while the majority of the others were not significantly or only weakly suppressed. BIC abolished or reduced the selectivity of all the orientation-selective cells while it did not affect any of the non-oriented cells tested. These results suggest that GABAergic inhibition already operates on a group of cortical neurons to make them orientation-selective at the time of eye opening.

Animals↗
PubMed1983

Postnatal development of corticotectal neurons in the kitten striate cortex: a quantitative study with the horseradish peroxidase technique.

Postnatal development of striate cortical neurons projecting to the superior colliculus (SC) was studied in cats, ranging in age from newborn to adult, by injection of horseradish peroxidase (HRP) into the SC. At birth HRP-labelled cells were widely distributed throughout the cortex between the splenial and suprasylvian sulci, although a very rough topographic correspondence seemed to exist between the striate cortex and SC. The labelled cells were confined to layer V of the cortex, as in the adult. They were very densely packed and their somas were already pyramidal in shape although very slender. During the third to eighth days, apical dendrites of a substantial number of cells, mostly located in the upper bank of the splenial sulcus, were filled with HRP up to layer I and their somas were larger than those of cells located near the crown of the lateral and postlateral gyri. At the eighth day and thereafter, the distribution of the labelled cells across the visual cortex was not so widespread as that seen in the newborn kittens. The dendritic arborization pattern of labelled cells became nearly adultlike at the four week, and its full maturation was seen at the eighth week. A quantitative analysis of the cross-sectional areas of the cells and their packing density in layer V of the cortex revealed that (1) the size of cells increased very rapidly during the second week and became almost adultlike at the fifth week; (2) the density of cells reduced dramatically during the second week and thereafter at a low rate until the eighth week; and (3) the ratio of the labelled to unlabelled cells in layer V decreased remarkably also during the second week. These results suggest that an elimination of axon collaterals of corticotectal cells or their death may take place mostly during the second week of age, when eye-opening occurs in kittens. By comparison with previous data on functional development of the SC, it is also suggested that the maturation of visual response properties of SC neurons may depend on postnatal development of corticotectal cells.

Animals↗
PubMed1983

Postnatal development of corticotectal neurons in the kitten striate cortex: an electrophysiological study.

In cats ranging in age from the second week to adult, the postnatal functional development of striate cortical neurons projecting to the superior colliculus (SC) was studied by observing their visual responses, axonal conduction velocities and spontaneous activities. One-hundred-and-fifty-seven cells were identified as projecting to the SC (C-T cells) on the basis of antidromic activation from SC. At the second week of age, 57% of the C-T cells had receptive fields of the complex type and the others were visually unresponsive. C-T cells with 'special complex' properties, which are characteristic of the adult C-T cells, first appeared at the third week and made up 19% of the total. The proportion of such C-T cells increased very rapidly and attained the adult-like value at the fourth week. The spontaneous activity of the C-T cells was very sparse or absent at the second week and increased thereafter with age. The proportion of cells with the high level of spontaneous activity found in the adult increased with the same time-course as did the special complex cells. The axonal conduction velocity of C-T cells was slower than 2 m/s until the third week. C-T cells with the faster velocities, suggestive of axonal myelination, appeared at the fourth week and thereafter the average value increased very rapidly until the weeks 8-9. These results indicate that the most remarkable functional development of C-T cells may occur around the fourth week of age. By comparison with previous data on postnatal development of neurons in the cortex and SC, we suggest that C-T cells may be one of the early-maturing groups of cells in the striate cortex and their maturation may exert a crucial influence on the development of visual response properties of SC neurons.

Aging↗
PubMed1982

Effects of stimulation of the dorsocaudal claustrum on activities of striate cortex neurons in the cat.

In the cat striate cortex, single electrical shocks applied to the dorsocaudal claustrum (CLdc) elicited bimodal excitatory responses with about 12 and 26 ms latencies. About one-fourth of the cortical cells observed had CLdc-induced inhibitions with onset latencies longer than the excitations. On cortical field responses to geniculate stimulation, CLdc conditioning shocks exerted early facilitatory and late inhibitory effects which were shown to be not transmitted through the mesencephalic reticular formation.

Animals↗
PubMed1982

Laminar differences in development of afferent innervation to striate cortex neurones in kittens.

We studied 587 cells in the striate cortex of 47 kittens, ranging in age postnatally from the 8th day to the 20th week, to explore differences in rates of functional maturation of cells and afferents among cortical layers. For all cells studied we determined spontaneous activity level, visual responsiveness, responsiveness to electrical stimulation of the afferent pathways and histologically reconstructed their laminar localization. At the 2nd-3rd week postnatally, single shocks applied to the dorsal lateral geniculate nucleus (LGN) elicited relatively inconsistent responses with long latencies in most of the cells in all layers, except in layer V where responses were consistent. In layers IVab, V, and VIu (the upper half of layer VI) the LGN-latency decreased very rapidly in the 4th week, while in layer IVc such a decrease occurred in the 5th week. In layers II+III and VIl (the lower half of layer VI) a less substantial decrease in latency occurred during the 4th and 5th week. At 2 weeks, nearly half of layer V cells had orientation-specific visual responses or spontaneous activity, but such cells were rare in other layers. The proportions of the specific or spontaneously active cells matured successively in the order of layers V leads to IVab and VIu leads to IVc leads to II+III and VIl. We conclude that the maturation of functional properties of cortical cells may occur successively in the above-mentioned laminar order, and that cells size and connectivity with afferents may be factors influencing the rate of functional maturation of cortical cells. The intracortical synaptic delay was estimated for each of the cells driven mono-synaptically from the LGN. The average delay decreased most rapidly during the 4th and 5th week. Conduction velocities of afferents innervating the mono-synaptic cells in layers IVab and IVc were calculated. The velocity of the former afferents increased very quickly and reached a value suggesting myelination at 4 weeks, while that of the latter afferents at 5 weeks. Since each type of LGN cell is known to project separately to layers IVab and IVc, respectively, this suggests that Y-cells of LGN may mature earlier than X-cells.

Aging↗
PubMed1982

Postnatal development of the corticofugal projection from striate cortex to lateral geniculate nucleus in kittens.

In kittens ranging in age from the eighth postnatal day to twentieth week, 288 striate cortex cells were identified as projecting to the dorsal lateral geniculate nucleus (LGN) on the basis of antidromic activation from LGN and of histological localization of cortical layer VI. These cells (C-G cells) were classified as complex, simple, or visually unresponsive, as in the adult. During the second-third postnatal weeks, most of the C-G cells were visually unresponsive. They often showed a marked step in the negative stroke of spikes evoked by single shock stimulation. When paired shocks with short intervals were applied, the second spike fractionated at the step to reveal the A and B components. This tendency was not observed at 8-9 weeks or later. At the second week, all the visually responsive cells were complex, while simple cells were recorded at 3 weeks or later. Until the fourth week, LGN-latencies of complex cells were very long (11-35 ms), although they were the shortest group at each age. Adult-like latencies were first observed at the fifth week in complex cells and at the eighth-ninth weeks in simple cells. The axonal conduction velocities of complex cells attained to the values suggesting myelination at the fifth week, while those of simple cells much later. These results suggest that complex C-G cells may mature prior to simple cells. By comparison with previous results it is also suggested that myelination of the retino-geniculo-cortico-geniculate projections may occur in a retinofugal order.

Aging↗
PubMed1981

Effects of strabismus on development of cortico-geniculate projections in the kitten.

In six kittens reared with surgically induced strabismus, three each of convergent and divergent types, we studied 208 striate cortex cells. Of these, 22 were identified as projecting to the dorsal lateral geniculate nucleus (LGN) on the basis of antidromic activation from LGN and of histological localization within cortical layer VI. We classified these cortico-geniculate cells according to their axonal conduction velocities which in normal cats, are generally grouped into slow, intermediate, or fast categories. Proportions and mean conduction velocities of slow and fast groups were approximately the same as in the normal cat, but the intermediate group was almost entirely missing with only one cell classified as such. Our results suggest that development of the intermediate group, which has previously been implicated in functional binocular vision, may be impaired selectively by strabismus.

Aging↗
PubMed1981

Ocular dominance in kitten cortex: induced changes of single cells while they are recorded.

We have monitored extracellularly individual neurons in the striate cortex of 4-week-old unparalyzed kittens with the aim of changing the ocular dominance of these cells during recording. To do this, we elicited conjugate eye movements using a bipolar stimulating electrode positioned in the internal medullary lamina (IML) of the thalamus. During electrical stimulation of this region, one eye was occluded and the other was visually activated with optimal stimuli. Receptive fields were studied subjectively and objectively and relative response strengths were assessed. Of 42 cells studied in detail, 62% underwent changes on ocular dominance following conditioning periods of, generally, 15-20 min. Control experiments suggest that this plasticity is: age-related; requires both visual stimulation and activation of pathways associated with eye movement; and does not appear to be caused solely by increased arousal levels.

Animals↗
PubMed1981

Effects of early monocular deprivation on development of cortico-geniculate projections in the cat.

In 16 cats monocularly deprived from 2 to 3 weeks of age, we studied 53 striate cortical cells which were identified as projecting to the dorsal lateral geniculate nucleus (LGN) on the basis of antidromic activation from LGN and of histological localization within cortical layer VI. As in the normal cat, these cortico-geniculate cells could be classified as slow, intermediate or fast, according to their axonal conduction velocities. The sampling ratio of the slow cells (mostly unresponsive to visual stimuli) was much higher than normal. On the other hand, the ratio of the intermediate (one half were simple cells) and fast cells (all except one were complex cells) was significantly lower than the norm. Also, the average axonal conduction velocities of the complex and simple cells were significantly slower than normal. These results suggest that normal maturation of cortico-geniculate cells, particularly fast and intermediate ones, is retarded or arrested by monocular visual deprivation.

Animals↗
PubMed1980

Three groups of cortico-geniculate neurons and their distribution in binocular and monocular segments of cat striate cortex.

Among 409 neurons recorded from binocular and monocular segments of the cat striate cortex, 91 were identified as cells (C-G cells) projecting to the dorsal lateral geniculate nucleus (LGN) on the basis of antidromic activation from LGN and of histological localization of cortical layer VI. The axonal conduction velocity of these C-G cells was calculated from differences in latency between antidromic responses to electrical stimulation of LGN and the optic radiation. According to this velocity, 70 C-G cells from the binocular segment could be classified as fast (13--32 m/sec), intermediate (3.2--11 m/sec) and slow (0.3--1.6 m/sec) cells. The fast cells (47% of the total) were spontaneously active and had receptive fields of complex type. Histologically they were located mostly in the upper half of layer VI. The intermediate cells (31%) were mostly simple. The slow cells (21%) were completely silent, not driven by visual stimuli, and located mostly in the lower VI. From the monocular segment of the cortex, the intermediate cells could not be recorded, while the other two groups of cells were sampled with the same frequency as from the binocular segment. These findings suggest an existence of three functionally distinct groups of C-G cells and a possible participation of the intermediate cells in binocular vision.

Animals↗
PubMed1979

Modification of orientation sensitivity of cat visual cortex neurons by removal of GABA-mediated inhibition.

The effects of an inhibitor of GABA synthesis, 3-mercaptopropionic acid (MP), and of the GABA antagonist bicuculline (BIC), on the direction and orientation sensitivity of visual cortical neurons were investigated using a computer-controlled stimulus presentation system. Intravenous administration of MP, which was usually more effective than if administered microelectrophoretically, induced a slight, but significant reduction in these properties of about half of the neurons tested. The effect of electrophoretic BIC was in the same direction but clearer than that of MP. In 71% of the simple cells, direction sensitivity was virtually lost during administration of BIC while orientation sensitivity was never completely eliminated in any neuron tested. Simultaneous administration of both drugs (MP systemically, BIC electrophoretically) caused more complete modification of the sensitivities than single administration of each. In four out of thirteen neurons tested, orientation sensitivity was completely abolished. The excitatory receptive fields slightly increased in size and became virtually round. The response magnitude to the optimal stimulus was increased by each drug along and by both. The present results further support the hypothesis that intracortical inhibition plays a major if not an exclusive role for the orientation and direction sensitivity of cortical cells.

3-Mercaptopropionic Acid↗
PubMed1978

Inhibitory and excitatory binocular convergence to visual cortical neurons of the cat.

Responses of 182 visual cortical (VC) neurons to electrical stimulation of both optic nerves (ON) were recorded intra- and extracellularly, and their eye dominance determined with visual stimuli. Many VC neurons could not be excited by ON stimulation without simultaneous activation by visual stimulation of the eye of the other side. The ON-excited units (25 simple and 71 complex cells) had essentially the same response latency from both ONs. In almost all VC neurons including those not driven from the ON, ON stimulation elicited inhibition which was shown to be post-synaptic in all neurons recorded intra- or quasi-intracellularly. The onset latency of IPSPs not preceded by an action potential or EPSP was 4.2+/-1.0 msec, suggesting that intracortical inhibition was initiated by afferent impulses mediated through fast conducting fibers. In visually monocular neurons, ON stimulation of the non-driving side also elicited primary inhibition. Visually binocular, but monocular-dominant neurons responded more reliably to ON stimulation of the dominant side than to the other. In most binocular neurons with equal visual responsiveness to both eyes, inhibition and excitation evoked from both ONs had about the same latency and magnitude.

Animals↗