Rigorous and extended application of information theory to the afferent visual system of the cat. I. Basic concepts

Information theory is applied to data from microelectrode recordings of the cat's afferent visual system in a manner more general than hitherto usual. It is shown that it is not necessary to know the particular neuronal code for information calculations by taking the signal itself as the symbols. Uncontrollable errors thus can be avoided. It is further shown that by this approach the dynamical behaviour of the system is fully considered for information transfer. Quantities are defined to exhibit the time course of transmitted information.     

Spinal control of afferent temperature information in the cat

The effect of picrotoxin (at sub-convulsant doses, i.v.) on the background and invoked spike activity of cat dorsal horn internerons was investigated while thermal and mechanical influences were at work on the skin receptor areas. It was found that information on skin temperature is modulated at the presynaptic level and largely mediated by competitive interaction between large and small diameter fibers.Institute of Physiology, Academy of Sciences of the Kazakh SSR, Alma Ata. Translated from Neirofiziologiya, Vol. 18, No. 6, pp. 773–779, November–December, 1986.     

Pathways for transmission of visual and auditory information to the cat caudate nucleus

Visual and auditory projections to the cat caudate nucleus were investigated using the horseradish peroxidase retrograde axonal transport technique in conjunction with that of experimental degeneration of retinal axons. It was found that visual information may reach the caudate nucleus not just through well-known polysynaptic pathways from the cerebral cortex but also following oligosynaptic (transpulvinar, lateroposterior nucleus, suprageniculate nucleus, and nucleus limitans of the thalamus) as well as bisynaptic pathways (via the medial and lateral terminal nuclei of the accessory optical tract, pulvinar, pretectum, intermediary layer of the superior colliculus, and the supraoptic nucleus); some of these pathways were identified for the first time. Direct retinal inputs were found in the suprageniculate nucleus. Additional structures were discovered through which auditory information may reach the caudate nucleus, i.e., the dorsal nucleus of the parvocellular portion of the lateral geniculate body, the deep-lying superior colliculus, and the dorsal and ventral nuclei of the lateral lemniscus. The physiological significance of the pathways described for possible transmission of visual and auditory impulses is discussed and a new principle underlining the organization of sensory inputs into the caudate nucleus is put forward.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 4, pp. 512–520, July–August, 1987.     

Conduction of excitation in the cat visual system

Unit responses in area 17 of the visual cortex to stimulation of the lateral geniculate body and optic tract were studied in experiments on unanesthetized cats immobilized with D-tubocurarine. Of the neurons tested, 53.6% responded to stimulation of the lateral geniculate body. In 92% of these cells the responses were orthodromic with latent periods of between 2 and 12.5 msec. Most cells responded with latent periods of 2.0–2.5, 3.0–3.5, and 4.0–4.5 msec, corresponding to latent periods of the components of the electropositive wave of the primary response. Antidromic responses to stimulation of the lateral geniculate body were given by 8% of neurons. The difference between the latent periods of responses of the same visual cortical neurons to stimulation of the optic tract and lateral geniculate body was 0.1–1.8 msec, but for most neurons (55.8%) it was 0.5–1 msec. The histograms of response latencies of visual cortical neurons to stimulation of the above-mentioned formations were found to be similar. It is concluded that the optic radiation contains three principal groups of fibers with conduction velocities of 28.5–16.6, 11.7–8.9, and 7.4–6.0 m/sec, respectively.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 7, No. 6, pp. 589–596, November–December, 1975.     

On the application of the information concept to learning theory

A learning curve derived by H. D. Landahl (Bull. Math. Biophysics,3, 71–77, 1941) from postulated neurological structures is shown to be derivable from simplified assumptions by introducing the information measure of the uncertainty of response. The possible significance of this approach to learning theory is discussed.     

An application of information theory to biological evolution

An evolving population of two alleles which generates another new allele is investigated within the framework of information theory. A communication system model of self-reproducing organisms which reproduce the genetic information by the self-reproduction is proposed and the concept of distortion when the genetic information is reproduced is introduced. What genetic information should be transmitted to the next generation? This question may be answered by so called rate distortion theory. The theory is applied to our model and the exact solution is obtained. Numerical results show that in low distortion region, new allele cannot survive, hence no evolution occurs; in intermediate distortion region, all alleles coexist; and in high distortion region, minor allele cannot survive. Moreover, diversity of the progeny takes its maximum value in the intermediate distortion region. This suggests that there may exist an optimal distortion for a population to evolve.     

Temporal correlations and coding of information in the visual cortex of the cat

We have observed repeated patterns in evoked spike trains recorded from the primary visual cortex of the cat. These patterns are called "triplets" and "ghost doublets". Triplets are groups of three pulses, that may or may not be adjacent to one other, the mutual intervals of which are replicated in one other group of three spikes with a precision higher than 0.15 ms. Ghost doublets are doublets of pulses whose interval replicates, with the above precision, one of the intervals of the repeated triplets and are also present in the record. In one of the 9 recorded cells, in which pulses were clearly emitted in bursts in phase with the drifting of the sinusoidal grating used as a stimulus, we could show that local temporal correlations in the form of replicating triplets and ghost doublets correspond very precisely to the temporal phase of the grating: the study of the distance between triplets, or between triplets and ghost doublets, gives a remarkably precise value of the time frequency of the grating.     

Role of interoceptive afferent excitation in sensory integration on neurons of the cat visual cortex

Experiments on cats immobilized with diplacin showed that stimulation of the vagus and splanchnic nerves had a significant effect on spontaneous unit activity in area 17 of the cortex. The unit responses most frequently observed were prolonged tonic changes in the discharge frequency. Complex phasic unit responses with stable inhibitory pauses and periods of activation occur less often. The development of phasic responses could begin either with a period of activation or with initial inhibition of activity. As a result of splanchnic nerve stimulation responses of predominantly excitatory type appeared. These also occurred more often in response to somatic stimulation. The degree of recruiting into the responses and the intensity of the responses themselves increased if a series of stimuli was applied to the nerves. The important role of the lateral hypothalamus and mesencephalic reticular formation in the mechanism of the visceral and somatic events observed on visual cortical neurons was demonstrated.Ivano-Frankovsk Medical Institute. Translated from Neirofiziologiya, Vol. 9, No. 4, pp. 361–368, July–August, 1977.     

Monomodal convergence in the visual system of the alert cat

In chronic experiments on waking cats, the interaction between signals evoked by simultaneous stimulation of the lateral geniculate body (LGB) and pulvinar was mainly of occlusive type which was more pronounced in the visual than in the associative cortical area. Conditioning stimulation of LGB depressed the response to testing stimulation of the pulvinar at delays of 10 ms. Delays of 20-60 ms facilitated the response. At short delays between the stimuli, the conditioning pulvinar stimulation either did not change significantly the response to testing LGB stimulation or facilitated it. At long (80-200 ms) delays the same conditioning stimulation produced a depression of the response to the testing stimulation. The results obtained point to monomodal convergence in the system of the cat visual analyzer and also to a relative autonomy and predominance of the cortical input from LGB and to dependence of pulvinar input functioning on the degree of activation of the geniculo-cortical path.     

A computer simulation model of the afferent part of the visual foveation system

It is argued that the duplicity notion of visual perception refers to two separate neural systems, the foveation and identification system. A computer simulation model for the afferent part of the foveation system was developed. It consists of a receptive matrix and a retinal, geniculate, and cortical network. Within the networks neurons were substituted by threshold gates. The retinal information of the model can be controlled by the geniculate network and is analyzed with regard to stimulus orientation and movement by hypercolumns of cortical gates. The implemented columnar organization preserves retinocortical continuity. Retinal and cortical information together provide the necessary prerequisites for the efferent part of the foveation system.Supported by a grant from the Deutsche Forschungsgemeinschaft     

Origins of the afferent fibers to the cat superior cervical ganglion.

The origins of the afferent fibers to the cat's superior cervical ganglion (SCG) were demonstrated by using the retrograde horseradish peroxidase tracing method. We found that the preganglionic neurons were located in the spinal segments C8-T5, particularly in T1-T3. These neurons were situated mainly in the intermediolateral column. The extra-SCG neurons along with the cervical sympathetic trunk originated ipsilaterally from the middle cervical and stellate ganglia, and contralaterally from the caudal part of the SCG. Labeled neurons also originated from the mandibular division of the trigeminal ganglion. Our results demonstrated that many fiber sources projected to the SCG, which plays a complicated synaptic role in controlling the visceral organs of the head and neck region.