An analysis of the interaction of the parietal and visual regions of the cortex with the posterior lateral nucleus of the thalamus]

Cooling and ablation of the parietal associative (P) and primary visual projection (VI) areas in nembutalized cats revealed facilitating and inhibitory descending influences of the above areas on the postero-lateral nucleus (LP) of the ipsilateral thalamus where visual signals generate an early specific and a late unspecific components of heterogenous evoked responses. Unidirectional influences activating the early component and fully controlling the appearance and course of the late component are more manifest in P which is a part of the same associative brain system as LP; they are less manifest in VI which belongs to the projection system. At later cooling stages the centrifugal influences of P and VI are sometimes of opposite signs; this effect is connected with reciprocal relations between projection and association systems and processes or selfcontrol within the association system. The corticofugal effects also participate in the common activity of P and VI taking place to a certain degree at the level of the LP which activates these cortical structures.     

Electrophysiological analysis of the functional organization of cortico-cerebellar connections

The effect of stimulation of cortical association (orbito-frontal, parietal) and projection (auditory, sensomotor) areas on the activity of Purkinje neurons of the cerebellar cortex was studied in adult cats anesthetized with pentobarbital, with or without chloralose. These responses were compared with those to peripheral stimuli. Definite similarity was found between the responses of Purkinje cells to different cortical (association and projection) stimuli as regards both the types of responses of the neurons and their ability to respond. No similarity was observed in the responses of Purkinje cells to peripheral (visual, auditory, electrodermal) stimulation. Whereas almost identical numbers of neurons (over 50%) were excited in response to the different forms of cortical stimulation, the ability of the neurons to respond to peripheral stimuli differed considerably: 44.6% of neurons responded to electrodermal stimulation, 34.2% to auditory, and 18.8% to visual.Medical Institute, Kemerovo. Translated from Neirofiziologiya, Vol. 8, No. 5, pp. 483–489, September–October, 1976.     

Multimodal spatial representations engaged in human parietal cortex during both saccadic and manual spatial orienting

BACKGROUND: Recent neuroimaging studies have found that several areas of the human brain, including parietal regions, can respond multimodally. But given single-cell evidence that responses in primate parietal cortex can be motor-related, some of the human multimodal activations might reflect convergent activation of potentially motor-related areas, rather than multimodal representations of space independent of motor factors. Here we crossed sensory stimulation of different modalities (vision or touch, in left or right hemifield) with spatially directed responses to such stimulation by different effector-systems (saccadic or manual). RESULTS: The fMRI results revealed representations of contralateral space in both the posterior part of the superior parietal gyrus and the anterior intraparietal sulcus that activated independently of both sensory modality and motor response. Multimodal saccade-related or manual-related activations were found, by contrast, in different regions of parietal cortex. CONCLUSIONS: Whereas some parietal regions have specific motor functions, others are engaged during the execution of movements to the contralateral hemifield irrespective of both input modality and the type of motor effector.     

Relationship between thalamic projections and different areas of the parietal association cortex in cats

Thalamic neuronal projections to the parietal association cortex were investigated in cats applying techniques of retrograde axonal transport of two fluorescent dyes (primuline and fast blue). The dorsal thalamic pulvinar (PL) as well as the dorsal and caudal lateral posterior nucleus (LP) were found to project mainly to the central suprasylvian gyrus (CSSG), while the ventral PL and the ventrorostral LP send out projections to rostral sites of the same gyrus (RSSG). Neurons with dual labeling were found in the PL, LP, suprageniculate, anteroventral, and ventrolateral thalamic nuclei following a single injection of two different markers into the RSSG and CSSG, as well as the centrolateral, paracentral, and centromedial nuclei. Topical organization of sources of cortical projections within the PL-LP complex can apparently provide a high level of discrimination of visual signals by individual cortical units. At the same time, the RSSG and CSSG appear to function in harmony to a considerable extent during integration of information of differing cortical origin; this could point to a lack of differentiation on the part of the RSSG and CSSG, corresponding to feline cortical areas 5 and 7 approximately.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 2, pp. 135–142, March–April, 1991.     

Organization of afferent inputs of the parietal association (area 7) and Clare-Bishop areas of the cat neocortex

Unit activity was recorded from two parietal areas of the cat neocortex in semichronic experiments. Cell responses to presentation of adequate stimuli of different modalities and to direct electrical stimulation of various cortical zones were studied. About 4% of neurons of the Clare-Bishop area did not respond to visual stimulation. Cells responding to stimuli of different modalities were found in the Clare-Bishop area. A high percentage of cells in this area responded to direct electrical stimulation of area 17. In the association area (area 7) 27% of neurons tested responded to visual stimuli, but only a very small relative number of cells (compared with responding neurons of the Clare-Bishop area) responded to stimulation of the primary sensory areas. Electrical stimulation of area 7 inhibited evoked and spontaneous unit activity in the Clare-Bishop area. The hypothesis that these areas are the association representation of two different sections of the visual system — retino-geniculocortical and retino-tecto-thalamocortical — is discussed.Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 13, No. 6, pp. 612–620, November–December, 1981.     

Neurophysiologic analysis of the bilateral organization of the associative parietal regions of the neocortex in the cat

In cats under Nembutal anesthesia, impulses come to the parietal areas of both hemispheres, which, when evoked by unilateral stimulation of fore- and hind-paws, converge at the same cortical points forming early components of associative responses (ECAR). In responses to contralateral paws' stimulation, individual interhemispheric functional asymmetry is shown. The influence of the contralateral parietal area on the ipsilateral one is more strong than the reverse effect. In contrast to ECAR formation on the contralateral side as a result of the arrival of impulses of specific genesis along the "classical" lemniscal tract,--the signals of the same type participating in the initiation of ECAR in the ipsilateral hemisphere, on their way form a relay in the thalamus and the same zone of the opposite side via the interthalamic commissure and callosal body, correspondingly. It is suggested that along with the arrival of impulses through the mentioned crossed tracts, ECAR generation in the ipsilateral parietal cortex involves impulses, coming through the uncrossed channel of the extralemnisc tract.     

Functional topography of afferent projections of the horizontal division of the nucleus of the diagonal band in the dorsolateral neocortex of the cat

EPs recording under Nembutal anaesthesia during stimulation of the medial section of the horizontal part of the diagonal band nucleus (HNDB) shows a wide spreading of HNDB afferentation over the neocortex: from the frontal area to the medial and some posterior parts of the auditory, parietal areas and Ep zone, with the least activation of the latter three regions and activation increasing intensity correspondingly in the somatic zones II, I (SII, SI), motor and frontal cortex. Such reduction of signals flow intensity oriented both in caudal and ventral directions of the cortex goes with foci of maximal activity of these signals in the motor, parietal areas and zones of representation of various body parts in SI and SII. Traits of similarity and differences of signal's projections in the neocortex from HNDB and thalamic relay nuclei have been revealed. A hypothesis is substantiated on different mechanisms underlying peculiarities of influences of these subcortical nuclei on the cortex depending on the type of their afferent-neuronal links in the latter and their functional role in the brain activity.     

A chronic experimental study to compare the electrocorticogram of certain brain areas in the drowsy cat

The spontaneous electrocorticogram of the first somatosensory (area 53), first auditory (area 22), visual (area 17), association (area 5), and second auditory (area 52) projection areas was studied in chronic experiments on drowsy unanesthetized cats. In the intermediate periods between waking and sleep and vice versa, maximal differences expressed as heterogeneity of the spindle component and low coefficients of cross correlation (0.21±0.04) were found in the slow-wave activity of the areas studied. During deepening of sleep the synchronization of the potentials recorded from the different areas increased and the coefficients of cross correlation rose to 0.40±0.18. The level of differences between the coefficients of correlation compared in the different phases of sleep was 0.19 and was significant by Student's criterion. It is postulated that functional changes in the thalamic pacemaker mechanisms take place during changes in the depth of sleep. In response to afferent stimulation of different modalities no differences were found in the desynchronization response in the projection areas. After extinction of the orienting reflexes and application of stimulation of adequate strength, specific differences in the development of the desynchronization response to adequate stimulation were found in the projection zones. The need for certain conditions being present before signs of specificity of the responses in the projection areas can be detected is emphasized.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 8, No. 6, pp. 583–596, November–December, 1976.     

Hearing in honeybees: the mechanical response of the bee's antenna to near field sound

In the dance language, honeybees use airborne near field sound signals to inform their nestmates of the location of food sources. In behavioral experiments it has recently been shown that Johnston's organ, a chordotonal organ located in the pedicel of the antenna, is used to perceive these sound signals. In the present study the mechanical response of the antennal flagellum to stimulation with near field sound signals was investigated using laser vibrometry. The absolute amplitudes of antennal deflection with acoustical stimulation, the response to sounds of different displacement and velocity amplitudes, the shape of movement of the flagellum, the mechanical frequency response and the mechanical directional sensitivity of the auditory sense organ of the honeybee are described. Using pulsed stimuli simulating the dance sounds it is shown that the temporal pattern of the dance sound is resolved on the level of antennal vibrations.     

The neuronal reactions of the cat motor cortex to electrical stimulation of the ventral tegmental area as a conditioned signal for the reflex of placing the forelimb on a support]

Electrical stimulation (50-100 pulses, 100-500 Hz) of the ventral tegmental area (VTA) in the vicinity of the n. interpeduncularis in the frontal plane AP2-AP4, L1-L2 caused a cat to grab food placed near its mouth. The conditioned forepaw placing reaction was elaborated using food reinforcement and VTA stimulation as a conditioned stimulus. The conditioned reflex, being once established, was repeatedly performed without extinction in the course of up to 250 trials without food reinforcement. Short (5-10 pulses) conditioned VTA stimulation evoked a prolonged (up to 1000 ms or longer) activation of neurons of the motor cortex and caused a substitution of the inhibitory phase of response to stimulation of the parietal cortex in poststimulus interval in 50-200 ms for the late secondary excitatory response.     

Increased activity in human visual cortex during directed attention in the absence of visual stimulation

When subjects direct attention to a particular location in a visual scene, responses in the visual cortex to stimuli presented at that location are enhanced, and the suppressive influences of nearby distractors are reduced. What is the top-down signal that modulates the response to an attended versus an unattended stimulus? Here, we demonstrate increased activity related to attention in the absence of visual stimulation in extrastriate cortex when subjects covertly directed attention to a peripheral location expecting the onset of visual stimuli. Frontal and parietal areas showed a stronger signal increase during this expectation than did visual areas. The increased activity in visual cortex in the absence of visual stimulation may reflect a top-down bias of neural signals in favor of the attended location, which derives from a fronto-parietal network.     

The effect of electric stimulation of different regions of the cerebral cortex on the alimentary reaction in rabbits]

The influences of different parts of the neocortex on the rabbit alimentary behaviour produced by stimulation of the hypothalamic "alimentary centre" were studied in chronic experiments on rabbits with electrodes implanted in different formations of the limbic system and the midbrain. It has been found that electrical stimulation of the frontal and anterior parietal cortical areas raised the threshold of the evoked alimentary reaction. Inhibitory influences of the frontal areas proved to be stronger and more prolonged than those of the anterior parietal area. Electrical stimulation of the posterior parietal and occipital cortical areas decreased the threshold of the evoked alimentary reaction. Coagulation of the dorsal hippocampus eliminated the inhibitory influences of the neocortex, while coagulation of the mesencephalic reticular formation discontinued the facilitating influences of the neocortex on the alimentary reaction.     

Involvement of visual specific and association cortex input in the shaping of neostriatal neuron response to visual stimulation in unanesthetized cats

During chronic experiments on unanesthetized cats neuronal response in the caudate nucleus to the presentation of local photic stimuli and electrical stimulation of the specific (field 17) and the association (Clare-Bishop) areas were compared. Stimulation of the Clare-Bishop area proved more effective than stimulating field 17 for neurons of the caudate nucleus; a response was produced in 47% of test neurons in comparison with 8% of units only in the specific area. Lower average values were observed for latency of neuronal response to stimulation of the Clare-Bishop area. An insignificant number of caudate nucleus neurons were activated as a result of stimulation of both cortical areas. A comparison between the response of one set of neurons to electrical cortical and visual stimulation showed that cells responding to visual stimulation were more highly activated by stimulating the Clare-Bishop area than by stimulation of field 17. This type of neuron predominated in the caudate nucleus. A discussion follows of the possible involvement of the Clare-Bishop area in shaping neuronal response to visual stimulation.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 17, No. 5, pp. 619–627, September–October, 1985.     

Influence of Anodal Transcranial Direct Current Stimulation (tDCS) over the Right Angular Gyrus on Brain Activity during Rest

Although numerous studies examined resting-state networks (RSN) in the human brain, so far little is known about how activity within RSN might be modulated by non-invasive brain stimulation applied over parietal cortex. Investigating changes in RSN in response to parietal cortex stimulation might tell us more about how non-invasive techniques such as transcranial direct current stimulation (tDCS) modulate intrinsic brain activity, and further elaborate our understanding of how the resting brain responds to external stimulation. Here we examined how activity within the canonical RSN changed in response to anodal tDCS applied over the right angular gyrus (AG). We hypothesized that changes in resting-state activity can be induced by a single tDCS session and detected with functional magnetic resonance imaging (fMRI). Significant differences between two fMRI sessions (pre-tDCS and post-tDCS) were found in several RSN, including the cerebellar, medial visual, sensorimotor, right frontoparietal, and executive control RSN as well as the default mode and the task positive network. The present results revealed decreased and increased RSN activity following tDCS. Decreased RSN activity following tDCS was found in bilateral primary and secondary visual areas, and in the right putamen. Increased RSN activity following tDCS was widely distributed across the brain, covering thalamic, frontal, parietal and occipital regions. From these exploratory results we conclude that a single session of anodal tDCS over the right AG is sufficient to induce large-scale changes in resting-state activity. These changes were localized in sensory and cognitive areas, covering regions close to and distant from the stimulation site.     

Reduced insulin secretion in response to nutrients in islets from malnourished young rats is associated with a diminished calcium uptake

Changes in (45)Ca uptake and insulin secretion in response to glucose, leucine, and arginine were measured in isolated islets derived from 4-week-old rats born of mothers maintained with normal protein (NP, 17%) or low protein (LP, 6%) diet during pregnancy and lactation. Glucose provoked a dose-dependent stimulation of insulin secretion in both groups of islets, with basal (2.8 mmol/L glucose) and maximal release (27.7 mmol/L glucose) significantly reduced in LP compared with NP islets. In the LP group the concentration-response curve to glucose was shifted to the right compared with the NP group, with the half-maximal response occurring at 16.9 and 13.3 mmol/L glucose, respectively. In LP islets, glucose-induced first and second phases of insulin secretions were drastically reduced. In addition, insulin response to individual amino acids, or in association with glucose, was also significantly reduced in the LP group compared with NP islets. Finally, in LP islets the (45)Ca uptake after 5 minutes or 90 minutes of incubation (which reflect mainly the entry and retention, respectively, of Ca(2+)), was lower than in NP islets. These data indicate that in malnourished rats both initial and sustained phases of insulin secretion in response to glucose were reduced. This poor secretory response to nutrients seems to be the consequence of an altered Ca(2+) handling by malnourished islet cells.     

Mechanisms of interaction between the parietal association and projection areas of the cat neocortex

Changes in evoked potentials in the first visual (VI), first somatic (SI), and parietal areas of the cortex during local cooling of each area were investigated under pentobarbital anesthesia. Two types of interaction were distinguished. Type I interaction was found in all areas in the early stages of local cooling and was reflected in a similar decrease in amplitude of evoked potentials in intact parts of the cortex. In the thalamic association nuclei — the pulvinar and posterolateral nucleus — somatic evoked potentials were unchanged but visual were transformed differently from those in the cortex. Type IIinteraction was found in the later stages of cooling and only between the association area and each of the projection areas. It was reflected in a greater change in amplitude of the evoked potentials and also in their configuration. In response to somatic stimulation in the early stage of type II interaction transformation of evoked potentials in the cortex took place sooner than in the nuclei; in the later stage it took place immediately after transformation of the "subcortical" evoked potentials. In response to photic stimulation transformations of cortical evoked potentials were always preceded by the corresponding transformations in the nuclei. It is suggested that type I interaction is formed by intercortical connections and type II by direct and subcortical relay connections. Differences in the role of the association area in interaction of types I and II when activated by stimuli of different modalities are discussed.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 10, No. 6, pp. 573–581, November–December, 1978.     

Study of the ancient tecto-thalamo-cortical pathway of the visual system in rats

Recording the evoked potentials and neuronal activity, electrophysiological studies have been made on tecto-thalamo-cortical tract in rats. The existence of a system of efferent projections in the superficial, visual layers of the superior colliculi was shown which are diffusely present in the nucleus lateralis posterior (n. LP), indicating low level of morpho-functional organization of this region of the dorsal thalamus in rats. In response to electrical stimulation of the n. LP, in laterocaudal parts of the visual system (fields 17 and 18a of the cortex) the evoked potentials of primary-negative polarity were observed which are associated mainly with the superficial (I--IV) cortical layers. Predominant representation of tecto-thalamo-cortical system in the laterocaudal visual area of the cortex indicates the tendency to separate representation (with respect to cortical areas and cortical layers) of retino-geniculate and retino-tecal visual systems in rats.     

Interrelations of the cerebral hemispheres in the cat in early stages of ontogeny

Multiple recording of transcallosal responses (TCRs) from different cortex areas has been carried out by means of acute experiments with immobilized and anesthetized kittens at the age of 1 to 30 days after birth. Homotopical TCRs in kittens at the age of 2-15 days appear earlier, are presented wider and reveal features of a greater maturity configuration and of amplitudinal-temporal parameters in association zone (parietal and sensorimotor) in comparison with projection zones (somatosensory, visual and auditory). Interhemispheric interrelations in association cortex of kittens are carried out not only by means of callosal but extracallosal system. In the course of animal developing in the parietal cortex the drain of the surface-positive oscillation moves from V to III layer and the drain of the surface-negative deviation remains at the level of II-III layers. The late component is registered up to the depth of III-IV layers, having the drain in I-II layers. In sensorimotor cortex the surface-negative oscillation has the drain in I-II layers, surface-positive--in III and V--VI layers. The interhemispheric asymmetry emerging from the moment of responses appearance is peculiar to TCRs of projection and association zones. In the first month of the postnatal development the asymmetry of positive and negative TCR oscillation amplitude has an individual character in sensorimotor cortex and a specific one--in parietal. The temporal parameters of TCR in association areas of the left hemisphere cortex are significantly shorter than of the right one. The data given testify to the possibility of interhemispheric interrelation realization and the presence of interhemispheric asymmetry in cat's brain on the early stages of postnatal ontogenesis.     

State-Dependent Changes in Auditory Sensory Gating in Different Cortical Areas in Rats

Sensory gating is a process in which the brain’s response to a repetitive stimulus is attenuated; it is thought to contribute to information processing by enabling organisms to filter extraneous sensory inputs from the environment. To date, sensory gating has typically been used to determine whether brain function is impaired, such as in individuals with schizophrenia or addiction. In healthy subjects, sensory gating is sensitive to a subject’s behavioral state, such as acute stress and attention. The cortical response to sensory stimulation significantly decreases during sleep; however, information processing continues throughout sleep, and an auditory evoked potential (AEP) can be elicited by sound. It is not known whether sensory gating changes during sleep. Sleep is a non-uniform process in the whole brain with regional differences in neural activities. Thus, another question arises concerning whether sensory gating changes are uniform in different brain areas from waking to sleep. To address these questions, we used the sound stimuli of a Conditioning-testing paradigm to examine sensory gating during waking, rapid eye movement (REM) sleep and Non-REM (NREM) sleep in different cortical areas in rats. We demonstrated the following: 1. Auditory sensory gating was affected by vigilant states in the frontal and parietal areas but not in the occipital areas. 2. Auditory sensory gating decreased in NREM sleep but not REM sleep from waking in the frontal and parietal areas. 3. The decreased sensory gating in the frontal and parietal areas during NREM sleep was the result of a significant increase in the test sound amplitude.