Unit discharges in the mediodorsal nucleus of the squirrel monkey evoked by electrical stimulation of the olfactory bulb.
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Acoustic Stimulation↗
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Excitation of units in marginal rim of trigeminal subnucleus caudalis elicited by tooth pulp stimulation.
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Animals↗
Sensory and motor representation in the cerebral cortex of the three-toed sloth (Bradypus tridactylus).
Cortical sensory receiving areas were studied in 32 specimens of the three-toed sloth, Bradypus tridactylus, using the evoked response technique and barbiturate anaesthesia. Somatotopic organization in the somesthetic first area (S-I) was shown to be similar to that reported in higher mammals. The area devoted to the representation of the forelimb was considerably larger than that for the remaining body parts. The second somatosensory area (S-II), showing bilateral representation without a precise topographical organization, was identified in the rostral portion of the ectosylvian gyrus. Visual and auditory projections, occupying restricted areas, were found along the caudal banks of the ectosylvian fissure. Electrically excitable cortical motor area was explored in 8 animals anesthetized with diallyl barbituric acid in urethane. The motor representation of the various body parts was shown to coincide with the sensory projections, demonstrating the existence in a Eutherian mammal of a sensorimotor amalgam, identical to that described in marsupials. These findings suggest that sloths display a primitive pattern of neural organization, and that the sensory motor amalgam is a generalized form of cortical organization of primitive Therian mammals.
Acoustic Stimulation↗
Unit responses to moving stimuli in area 18 of the cat.
In paralyzed cats units were recorded from the peripheral projections on area 18. Of 46 cells, 71 percent responded to moving visual stimuli. From this sample 91 percent responded to velocities ranging from 5 to 400 degrees-sec(-1). Within this group, two classes of neurons could be distinguished. The first class had small receptive fields and responded repetitively to a moving grating. They had low spontaneous activity and were located in the superficial cortical layers. Random pattern movement elicited no response. The second class had large receptive fields and higher spontaneous activity. These neurons, found in the deeper layer of the cortex, responded better to slits than to grating. Responses to random pattern motion reached 50-100 percent of grating motion responses. A similar distinction holds for fast movement sensitive neurons of area 17. The identification of both these classes with simple and complex cells is discussed.
Animals↗
Operant control of pyramidal tract neurons: the role of spinal dorsal columns.
A monkey was trained to control the firing patterns of precentral pyramidal tract neurons. The operant task was for the monkey to produce consecutive interspike intervals (ISI) within a requisite range, or target. The mean time off-target (error) is used to quantify the accuracy of control the monkey could assert over each PTN. Following partial destruction of the dorsal funiculi the number of PTNs driven by peripheral stimuli greatly decreased. Those PTNs which remained responsive to peripheral stimuli were as accurately controlled as those tested before column section, whereas, those PTNs unresponsive to peripheral stimuli were significantly less accurately controlled. The conclusion is that the monkey relies heavily upon proprioceptive feedback to operantly control precentral PTNs.
Acoustic Stimulation↗
Interactions of inputs from dorsal columns and ventral tracts with visual inputs on single neurons of cat superior colliculus.
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Acoustic Stimulation↗
Sensory stimuli differentially affect in vivo nigral and striatal [3H]serotonin release in the cat.
The effect of auditory, visual and peripheral nerve stimulation on in vivo [3H]serotonin release in both caudate nuclei and substantiae nigrae was studied in either awake 'encéphale isolé' or halothane-anesthetized cats. Release of endogenously synthesized [3H]serotonin was estimated in each brain structure, using push--pull cannulae, continuously superfused with [3H]tryptophan. Bilateral and simultaneous application of click noises and light flashes to awake 'encéphale isolé' cats enhanced [3H]serotonin release in both substantiae nigrae but was without effect on striatal [3H]serotonin release. Unilateral, low intensity electrical stimulation of the forepaw of halothane-anesthetized cats diminished [3H]serotonin release in both caudate nuclei and the ipsilateral substantia nigra. No effect was observed in the contralateral substantia nigra. In contrast, high-intensity electrical stimulation of one forepaw increased [3H]serotonin release in the ipsilateral substantia nigra but was without significant effect on release in the other brain areas examined. The results are discussed in light of previously known anatomical data concerning serotoninergic pathways and electrophysiological evidence of the effect of sensory stimuli on serotoninergic neurons. Our findings suggest that serotonin neurons may serve an important function in the integration of sensory information.
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Participation of precentral neurons in somatically and visually triggered movements in primates.
Monkeys were trained to perform somatically and visually triggered wrist flexion-extension (F-E) movements. Extracellular unit recordings were made in the contralateral precentral forelimb area. These neurons were identified as being best related to particular single forelimb joints by their responses to passive somatosensory stimulation and to the determining effects of local intracortical microstimulation. It was found that almost 60% of single-joint related cells participated in both somatically and visually triggered movements. All wrist (F-E) neurons responded reciprocally while non-wrist (F-E) neurons had reciprocal as well as bidirectional responses to the oppositely directed visual and somatic perturbations. Somatically related responses and visually related responses were both uniformly distributed throughout the vertical layers of precentral cortex. With respect to horizontal spatial arrangements, multiple clusters of reciprocally and bidirectionally responsive neurons were intermingled. This latter finding supports the concept of a context-sensitive organization for motor control within precentral cortex.
Animals↗
Functional activity of rat brainstem neurons regenerating axons along peripheral nerve grafts.
To investigate activation and discharge patterns of central nervous system neurons that regenerate lengthy axons along peripheral nerve grafts we inserted a 4 cm long autologous segment of sciatic nerve into the dorsolateral medulla oblongata of adult rats. Two to 6 months after grafting, the distribution of the cells of origin of the regenerating axons in many nuclei of the brainstem was documented by retrograde horseradish peroxidase labelling from the cut end of the grafts. Functional properties of neurons regenerating axons into the grafts were studied by recording from single regenerated fibers teased from the grafts. Conduction velocities of graft fibers ranged from less than 1 m/s to 25 m/s (30 degrees C). Spontaneous centrifugal impulse traffic in the grafts included units firing in bursts synchronously with the respiratory cycle. Activity in other units was either elicited or inhibited by natural or electrical stimulation of the periphery. Most units recorded in the grafts were neither spontaneously active nor responsive to stimulation of primary afferents. We conclude that: there are central nervous system neurons projecting into the grafts that respond to both excitatory and inhibitory transsynaptic influences; at least some of the spontaneous and induced activity recorded from axons in the grafts resembles that known for normal nerve cells in the regions of the brainstem from which axonal growth arises; and it is possible that many central neurons regenerating axons into peripheral nerve grafts have significantly reduced or altered synaptic inputs.
Animals↗
W-like response properties of interlaminar zone cells in the lateral geniculate nucleus of a primate (Galago crassicaudatus).
Recent anatomical studies have suggested that the cells located in the interlaminar zones (ILZs) of the primate dorsal lateral geniculate nucleus (LGN) relay visual information from the retina to the striate cortex in a manner similar to that of W-cells in the LGN of cat. In the present study, we examined this idea directly by recording the response properties of single cells localized to the ILZs in the prosimian primate, Galago crassicaudatus. The properties of the cells in the ILZs were found to be physiologically distinct from the X-like and Y-like properties of the parvocellular and magnocellular LGN layers. Moreover, the small cells located in the interlaminar zones were physiologically similar to the W-like cells found in the specialized small-celled koniocellular layers in these primates. As is the case with the koniocellular layer cells, the ILZ cells exhibited a broad range of properties which, as a group, were distinguished by the following characteristics: the ILZ cells had long latencies to stimulation of the optic chiasm (mean, 3.95 ms) and to antidromic stimulation from striate cortex (mean, 3.31 ms) and had relatively large receptive-field centers (mean, 1.79 degrees). They also had low maintained discharge rates (5.5 spikes/s), relatively long response latencies to light (mean onset, 82 ms; peak, 112 ms) and low peak firing rates (59 spikes/s). Few (25%) had standard receptive-field organization (ON-center, OFF-surround, or vice versa). Only 29% responded well to sine-wave gratings and all were influenced by non-visual (auditory and tactile) stimuli.(ABSTRACT TRUNCATED AT 250 WORDS)
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Effect of noxious somesthetic stimulation on the activity of neurons of the nucleus centralis of the amygdala.
Neurons (n = 107) were recorded, in anaesthetized rats, with extracellular micropipettes, in the nucleus centralis of the amygdala (Ce). The activity of a large majority (77%) was exclusively or preferentially affected by noxious stimuli applied in any area of the body. The rest of the neurons was not activated by any stimuli (21%) or responded only to innocuous stimuli (2%). The nociceptive neurons were classified into two groups: the neurons in the first group (34% of the whole population) were activated by mechanical and thermal noxious stimuli; the neurons in the second group (43% of the whole population) were inhibited by noxious stimuli. Neurons in two groups precisely encoded thermal stimuli in the noxious range. Transcutaneous electrical stimulation suggested that the Ce nociceptive neurons were under the influence of A delta and C fibers. These results demonstrate important nociceptive input to the Ce which according to previous studies probably relays in the pontine parabrachial nucleus. In addition, they are in good agreement with the involvement of the amygdala in emotional, autonomic and/or behavioral reactions to noxious events.
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Selective involvement of the spinal trigeminal nucleus in the conditioned nictitating membrane reflex of the rabbit.
These experiments were performed to test the hypothesis that a region associated with the trigeminal nuclear complex is selectively involved in mediating the classically conditioned nictitating membrane reflex in the rabbit. Microinjections of Lidocaine were used to produce a temporary, localized block of neural activity following the conditioning of the reflex using a standard tone/air puff-paired stimulus paradigm. Data indicate that the injection of Lidocaine at the medial pars oralis/reticular formation junction results in a selective suppression of the conditioned reflex.
Animals↗
Oral nociceptive activity in the rat superior colliculus.
Single units were recorded using extracellular glass microelectrodes in all laminae of the superior colliculus of the rat under halothane nitrous oxide anaesthesia. Fifty-one units were encountered which responded to a low intensity mechanical stimulus applied to a contralateral or bilateral field located in the oral sphere (intraoral 11, perioral 16), on the face (29) or on the rest of the body (21). Sixteen units responded to a jaw movement. Sixty-one cells were recorded which were preferentially (10) or only (51) activated (30) or inhibited (21) by noxious stimuli. Contralateral or bilateral mechanoreceptive fields located in intraoral (34) and perioral (35) areas were frequent. There is therefore a high incidence of the nociceptive representation of the mouth in the superior colliculus. The other functional properties of the nociceptive units were similar to those reported in other studies. From the subsequent histological localization of the recorded units, it appeared that the nociceptive projections from the intraoral and perioral regions to the superior colliculus reach the lateral part of the intermediate and deep layers of the superior colliculus.
Anesthesia↗
Convergence of multi-modal sensory signals at thoracic interneurons of the escape system of the cockroach, Periplaneta americana.
Research on the escape system of the cockroach has focused upon the role of giant interneurons in conveying information on wind stimulation from the cerci located on the abdomen to motor control centers in the thoracic ganglia. In the thoracic ganglia the ventral giant interneurons connect to a population of interganglionic interneurons referred to as type A thoracic interneurons. In this paper we have tested the type A interneurons for additional sensory inputs in the absence of ventral giant interneuron activity. We find that the cells that receive ventral giant interneuron activity are also influenced by a variety of additional sensory inputs; wind mediated activity in a pathway that descends from the head, tactile inputs from several loci, auditory stimuli and light responses. Moreover, behavioral observations indicate that at least some of these activities can alter the escape movements. The results suggest that these interneurons serve as a site of convergence for numerous types of sensory activity. They further suggest that the escape system is capable of responding to directional wind information encoded in the ventral giant interneurons in the context of a wealth of additional information.
Animals↗
A modality-specific somatosensory area within the insula of the rhesus monkey.
Response properties of neurons in the monkey's granular insula (Ig) were examined with somatic, auditory, visual, and gustatory stimuli. Results indicate that a major portion of Ig is a somatic processing area exclusively, with units that have large and often bilateral receptive fields, consistent with the view that this area serves as a higher-order, modality-specific link in the somatosensory-limbic pathway.
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Polymodal sensory and motor convergence in substantia nigra neurons of the awake monkey.
Responses of substantia nigra (SN) pars compacta (SNc) and reticulata (SNr) neurons to sensory stimulation and movement were investigated in awake Macaca fascicularis. Concern was assigned to polysensory and sensory/motor convergence on the same cell, which were found in 12% and 9% of the neurons, respectively. Others were modality specific (35%) or unresponsive (44%). The convergence lends support to the notion that SN plays an important role in sensory-motor integration.
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Effects of chronic sleep deprivation on central cholinergic receptors in rat brain.
Rats subjected to chronic total sleep deprivation (TSD) by the disk-over-water method have shown very large, sustained rebounds in paradoxical sleep (PS) (also known as REM sleep). Other studies have indicated that cholinergic mechanisms are involved in the instigation and maintenance of PS. Hypothetically, the large PS rebounds could be mediated by an upregulation of cholinergic receptors during TSD. To evaluate this hypothesis, regional brain cholinergic receptors were compared in rats subjected to 10-day TSD by the disk-over-water method (TSD rats), yoked control (TSC) rats which received the same physical stimulation but with much smaller reductions in sleep, and home cage control (HCC) rats. L-[3H]nicotine and [3H]quinuclidinyl benzilate were used as specific cholinergic radioligands for nicotinic and muscarinic receptor binding assays, respectively. Nicotinic receptor binding was not significantly different among groups for any of the brain regions assayed, including frontal cortex, parietal cortex, thalamus, amygdala, hippocampus, anterior hypothalamus, posterior hypothalamus, caudate, limbic system (including septal area, olfactory tubercle, and nucleus accumbens), midbrain, pons, and medulla. Thus, there was no evidence that changes in nicotinic receptors mediate the PS rebounds. For muscarinic receptor binding, TSD rats differed significantly from control rats only in showing a higher binding affinity than TSC rats in the limbic system and a lower binding density than HCC rats in the hippocampus. On the other hand, significant differences in muscarinic receptor binding sites between rats selectively deprived of PS and their yoked controls were found only for the septal area.(ABSTRACT TRUNCATED AT 250 WORDS)
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Behavioral and pharmacological modulation of ventral tegmental dendritic dopamine release.
The mesocorticolimbic dopamine (DA) system is thought to comprise part of a neural substrate participating in behavioral reinforcement. While much emphasis has been placed on mesolimbic terminal field activity, the existence of somatodendritic DA release has also been established. In the present study, the release of endogenous DA from the ventral tegmental DA cell body region of freely moving rats was measured, using in vivo chronoamperometry after presentation of several environmental stimuli. While presentation of a 9-s moderately intense light stimulus did not significantly modify DA release, palatable food presentation (FD), 3 min of social interaction (SI) with another male rat and a 3-min tail-pinch (TP) produced an increase in electrochemical signal, suggesting an increase in somatodendritic DA release. Mean peak signal increases (calibrated in nM DA concentration) were 104, 135 and 161 nM after FD, SI and TP stimulus, respectively. After daily presentation of all four stimuli, one of four DA active drugs was given s.c. When compared with preinjection baseline, apomorphine (APO) caused a decrease while nomifensine (NOMI), cocaine (COC) and haloperidol (HALO) caused an increase in electrochemical signal. When TP was given 30 min after drug injection, APO, NOMI and COC suppressed the TP-induced signal increase compared with the predrug response. HALO, on the other hand, did not alter TP-induced DA release. These data support the hypothesis that the cells of origin of the mesocorticolimbic system release dendritic DA after physiologically relevant stimuli.
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