Unit responses of the secondary somatosensory cortex during defensive conditioning in cats

Unit responses in the secondary somatosensory cortex during the formation and extinction of a defensive conditioned reflex to acoustic stimulation were investigated in chronic experiments on cats. In 21 of 28 neurons tested during defensive conditioning the firing pattern changed in accordance with the character of responses to electric shock reinforcement. Two types of conditioned-reflex unit responses were distinguished: excitatory and inhibitory. Most neurons responding to the conditioned stimulus by activation did so during the first 50 msec, which was 80–100 msec before the conditioned motor response. Considerable variability of the unit responses was observed during conditioning. By the time of stabilization of the conditioned-reflex connections the unit response to the conditioned stimulus was stable in form. The pattern of extinction of the conditioned unit activity was expressed as a decrease in the discharge frequency in responses of excitatory type and disinhibition of activity in the case of inhibitory responses.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev, Translated from Neirofiziologiya, Vol. 9, No. 3, pp. 232–238, May–June, 1977.     

8-OH-DPAT对大鼠体感皮质5-羟色胺抑制单位自发放电的抑制作用

目的：研究5-羟色胺（5-HT）对大鼠大脑皮质第一体表感觉区自发单位放电（SI-SUD）的影响,以及5-HT1A受体在5-HT抑制SI-SUD中的可能作用。方法：记录微电泳5-HT及5-HT1A受体选择性激动剂8-OHDPAT前后的SISUD,分析：MISISUD的平均放电间隔（MISI）变化并作统计学处理。结果：①微电泳5-HT对SISUD的影响有3种情况：则MISI增大（抑制作用）（48／96）;MISI减小（兴奋作用）（26／96）或MISI无明显改变（无明显影响）（22／96）。其中以抑制作用为主。②在20个5-HT押制单位中,微电泳8-OH-DPAT可抑制其中17个单位的SISUD,而其余3个单位的SISUD无明显改变。结论：5-HT对SISUD的影响以抑制作用为主。体感皮质的大部分5-HT抑制单位存在有5-HT1A受体,并参与5-HT对SI-SUD的抑制作用。     

Unit responses of the auditory cortex of waking cats at rest and after defensive conditioning

In chronic experiments with glass microelectrodes responses of 288 spontaneously active neurons in the auditory cortex were investigated in cats at rest (123 neurons) and after defensive conditioning to sound (165 neurons). In the first situation 43% of neurons did not respond to acoustic stimulation. Most (about 60%) responses of the reacting neurons showed marked inhibition. Conditioning caused an increase (up to 72%) in the number of neurons responding to acoustic stimulation, the appearance of tonic responses, a severalfold increase in the amplitude of the responses, an increase in the number of responses of activation type, and stabilization of their form. The results point to increased excitability of neurons in this cortical area.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 11, No. 1, pp. 25–34, January–February, 1979.     

Mastication-related neurons in the orofacial first somatosensory cortex of awake cats

In the orofacial area of the first somatosensory cortex (SI), we recorded single unit activity from 699 neurons in 11 awake cats. Fifty-two percent (362/699) were mastication-related neurons (MRNs) showing activity related to some aspects of masticatory movements. MRNs were divided into three types by their activity patterns: (1) the rhythmical type, showing rhythmical bursts in pace with the masticatory rhythm; (2) the sustained type, showing a sustained firing during the period of taking food and (3) the transient (biting) type, showing intense discharges in coincidence with biting hard food. MRNs had mechanoreceptive fields in the perioral, tongue, periodontal and mandibular regions. The activities of perioral rhythmical-MRNs, mandibular transient-MRNs, tongue rhythmical-MRNs and periodontal transient-MRNs were correlated with food texture, while perioral rhythmical-MRNs, perioral sustained-MRNs and tongue sustained-MRMs were not. Both facial and intraoral MRNs were scattered throughout the facial and intraoral projection areas in SI. These findings provide evidence that the orofacial SI monitors masticatory movements for food ingestion.     

Analysis of the dependence of respiratory data during spontaneous ventilation at rest

Inspiratory duration (TI), cycle duration (TTOT), and tidal volume (VT) were continuously measured in 11 normal subjects during 400 respiratory cycles. Small breath to breath changes in these variables were separately analyzed. For each of these variables, successive observations are not statistically independent; "large" values tend to be followed by "large" values. A respiratory feedback may be involved in this sequential dependence. In that case, any known system of respiratory control could be associated with it, even those with time constant or delay longer than one cycle duration.     

The function of sensory information from the first somatosensory cortex for facial movements during ingestion in cats

The aim of the present study was to investigate the relationship between the facial region of the first somatosensory cortex (facial SI) and facial region of the motor cortex (facial MI), as the basis of orofacial behaviors during ingestion of fish paste. Area M in the ventral cortex of the cruciate sulcus that was defined as part of the facial MI by Hiraba et al. (1992 and 1993), showed various facial twitches evoked by intracortical microstimulation (ICMS) and recorded many mastication-related neurons (MRNs). Many MRNs in area M had receptive fields (RFs) in lingual, perioral and mandibular regions. The 60% value of activity patterns of MRNs (n?=?124) recorded in area M of normal cats, were the pre-SB type (the sustained and pre-movement type) that showed increased firing prior to the start of mastication and then tonic activity during the masticatory period. MRNs recorded in area M of cats with the facial SI lesion, showed a noticeable decrease in MRNs with RFs in the perioral and mandibular regions and with activity of the pre-SB type. These results strongly suggest that blocking facial SI sensory inputs evoked by mastication interferes with the relay of important facial sensory information to area M required for the appropriate manipulation of food during mastication.     

The function of sensory information from the first somatosensory cortex for facial movements during ingestion in cats

The aim of the present study was to investigate the relationship between the facial region of the first somatosensory cortex (facial SI) and facial region of the motor cortex (facial MI), as the basis of orofacial behaviors during ingestion of fish paste. Area M in the ventral cortex of the cruciate sulcus that was defined as part of the facial MI by and, showed various facial twitches evoked by intracortical microstimulation (ICMS) and recorded many mastication-related neurons (MRNs). Many MRNs in area M had receptive fields (RFs) in lingual, perioral and mandibular regions. The 60% value of activity patterns of MRNs (n = 124) recorded in area M of normal cats, were the pre-SB type (the sustained and pre-movement type) that showed increased firing prior to the start of mastication and then tonic activity during the masticatory period. MRNs recorded in area M of cats with the facial SI lesion, showed a noticeable decrease in MRNs with RFs in the perioral and mandibular regions and with activity of the pre-SB type. These results strongly suggest that blocking facial SI sensory inputs evoked by mastication interferes with the relay of important facial sensory information to area M required for the appropriate manipulation of food during mastication.     

Somatotopy of human hand somatosensory cortex as studied in scalp EEG

We recorded somatosensory evoked potentials (SEPs) in scalp EEGs during stimulation of the median nerve, the ulnar nerve and the individual digits in 3 normal subjects and in 1 epilepsy patients. In this patient we also measured SEPs from chronically indwelling subdural grid electrodes during electrocorticography (ECoG). We applied dipole modelling techniques to study the 3-dimensional intracerebral locations and time activities of the neuronal sources underlying stimulation of different peripheral receptive fields. The sources underlying median nerve SEPs were located an average of 10.8 mm lateral inferior to those underlying ulnar nerve SEPs. Digit SEP sources showed a somatotopic arrangement from lateral inferior to medial superior in the order thumb, index finger, middle finger, ring finger and little finger, with some overlap or reversal for adjacent digits. The average distance between thumb and little finger was 12.5 mm. Thumb, index finger and middle finger were clustered around median nerve cortical representation, whereas ring finger and little finger were arranged around ulnar nerve cortex. In the epilepsy patient, the source localizations obtained in scalp EEGs showed good agreement with those on ECoGs. We conclude that SEPs recorded in scalp EEGs can be used to study functional topography of human somatosensory cortex non-invasively.     

Relation of unit spike discharges and evoked potentials in the auditory cortex of cats.

Extracellular microelectrode recordings were made from the auditory cortex of anaesthetized cats during acoustic click stimulation. The microelectrode of low resistance allowed to record evoked field potentials and unit discharges simultaneously. In distant extracellular leads the relation of unit discharges and field potentials was equivocal. Near extracellular leads revealed that the antidromic invasion of the somadendritic membrane by excitation is a frequency dependent process (just as evoked field potentials) while spike potentials can reliably be elicited from the initial segment at high frequencies. It is assumed that the excitation spreading from the initial segment to the soma-dendritic membrane represents an important component of the evoked potentials, and their frequency dependence may be traced back to inhibitions activated by afferent impulses.     

State-dependent effects of light-dark cycle on somatosensory and visual cortex EEG in rats

Somatosensory (SSctx) and visual cortex (Vctx) EEG were evaluated in rats under a 12:12-h light-dark (LD) cycle and under constant light (LL) or constant dark (DD) in each sleep or wake state. Under LD conditions during light period, relative Vctx EEG slow-wave activity (SWA) was higher than that of the SSctx, whereas during dark period, relative Vctx EEG SWA was lower than in the SSctx. These effects were state specific, occurring only during non-rapid eye movement sleep (NREMS). Under LL conditions, the duration of REMS and NREMS during the period that would have been dark if the LD cycle had continued (subjective dark period) was greater than under LD conditions. DD conditions had little effect on the duration of NREMS and REMS. SSctx and Vctx EEG SWA were suppressed by LL during the subjective dark period; however, the degree of Vctx SWA suppression was smaller than that of the SSctx. DD conditions during the subjective light period enhanced SSctx SWA, whereas Vctx SWA was suppressed. Under LL conditions during the subjective dark period, Vctx EEG power was higher than that of the SSctx across a broad frequency range during NREMS, REMS, and wakefulness. During DD, SSctx EEG power during NREMS was higher than that of the Vctx in the delta wave band, whereas SSctx power during REMS and wakefulness was higher than that of the Vctx in frequencies higher than 8 Hz. We concluded that the SSctx and Vctx EEGs are differentially affected by light during subsequent sleep. Results provide support for the notion that regional sleep intensity is dependent on prior regional afferent input.     

Spontaneous activity of auditory cortical neurons of waking cats at rest and during defensive conditioning

The results of a computerized statistical analysis of 366 realizations of spontaneous spike activity of 181 neurons in the primary auditory cortex (area 50) of waking cats at rest and during defensive conditioning are described. In both situations the parameters of spontaneous activity of most neurons differed from those of a random flow. Conditioning led, on the one hand, to a stable increase in the frequency of spontaneous activity in intertrial periods and, on the other hand, judging from changes in the mean firing rate, the coefficients of variation of the length of the interspike intervals, the histograms of their distribution, and also the increase in the number of neurons with different forms of correlation between interspike intervals, to an increase in its stability (degree of organization).A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 10, No. 3, pp. 227–238, May–June, 1978.     

Horseradish peroxidase-positive neurons of nonspecific thalamic nuclei projecting to the primary somatosensory cortex in cats

The morphology and topography of neurons whose axons form the nonspecific thalamic input in the primary somatosensory area were studied in the cat forebrain by the retrograde axonal horseradish peroxidase transport method. Stained cells were found in the dorsolateral part of the nucleus ventralis anterior, and were diffusely distributed in the nucleus centralis, lateralis, the lateral part of the nucleus dorsalis medialis, and the dorsal part of the centrum medianum. In the nucleus paracentralis only solitary, palely stained neurons were detected. Cells stained with horse-radish peroxidase were multipolar, triangular, or fusiform. The results are evidence that besides the ventrobasal complex, the nonspecific nuclei of the diencephalon also project into the somatosensory cortex. This indicates the existence of multiple afferent thalamic inputs into the somatic cortex.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 11, No. 5, pp. 435–440, September–October, 1979.     

Changes in pain sensitivity after the ablation of the somatosensory areas of the cerebral cortex in cats

The effects of ablation of the first and second somatosensory cortex on pain sensitivity were studied in the behavioural experiments on adult cats. The ablation of the first somatosensory cortex (SI) was shown to cause an increase of the response thresholds at all the levels of a conventional scale, while the destruction of the second somatosensory cortex (S2) decreased the response thresholds. The role of SI and S2 in the evaluation of nociceptive information is discussed.     

Responses of cells in the somatosensory cortex of unanaesthetized cats after sinusoidal displacements of single vibrissae

Summary Neurones in the somatosensory cortex of unanaesthetized restrained cats were recorded during single trapezoid and repetitive sinusoidal displacements of single vibrissae. Responses to trapezoid displacements were similar to those described previously in anaesthetized cats (Hellweg et al., 1977).During repetitive mechanical stimulation cortical cells showed adaptive behaviour so that at higher stimulation frequencies the number of cell discharges per stimulus cycle decreased. The ability to follow the repetition of the stimulus at a one to one ratio was lost in the frequency range between 20 Hz and 60 Hz. A few exceptional cells, while not following at a one to one ratio, still showed some periodicities in their response histograms corresponding to repetition rates of up to 100 Hz. In about 10% of the cells nonmonotonic functions between stimulation frequency and response per cycle were found. These nonmonotonic functions as well as the different adaptive behaviour of cells could not be predicted on the basis of their response to trapezoid stimuli.Measurements of the phase differences between stimulus cycle and response peaks during repetitive stimulation showed that both can vary as a function of stimulation frequency. It is discussed whether these findings could be compatible with the concept of phase coding in the somatosensory cortex.