Electrophysiological and sensory properties of the thalamic reticular neurones related to somatic sensation in rats.

Abstract

SUMMARY1. In urethane-anaesthetized rats, studies were made on unit discharges of neurones of the thalamic reticular nucleus (tr) receiving the somatosensory input. Such units were found distributed in a part of the tr (s-tr) surrounding the anterior and anterolateral borders of the ventrobasal nuclear complex (vb).2. A series of five to ten bursts of grouped discharges were elicited in the s-tr neurones as orthodromic responses to single shock stimulation of the medial lemniscus (ml) or the somatosensory cortex (smc). In contrast to this, the vb relay cells were fired by ml impulses only once at short latencies, though later there occurred a series of two to three bursts of grouped discharges. The same response pattern was seen by stimulating the smc, except that the initial response to smc shocks was of antidromic origin.3. The mean response latency of the s-tr neurones to ml shocks was about 0-6 msec longer than that of the vb relay cells. Ml fibres connected to the s-tr neurones had the same distribution of conduction velocity as those connected to the vb relay cells. It is suggested that most, if not all, of the s-tr neurones are innervated by axon collaterals of the vb relay cells.4. About half the s-tr units were activated from vibrissae. For most of the remaining half either movements of hairs or touch to the skin were effective. In the vb, the units discharged by movements of hairs were most numerous and those activated from vibrissae were less frequent. While responses of the s-tr neurones to adequate stimuli were almost exclusively of phasic type, 30 % of the responses of the vb relay cells were tonic and the remainder were phasic.5. By exploring the tr extensively, the s-tr was found to be contiguous caudally to the perigeniculate reticular nucleus which is immediately adjacent to the dorsal lateral geniculate nucleus and contains reticular neurones activated by visual stimuli. Though few in number, units were found in the tr which received a convergence of somatosensory and visual inputs or of somatosensory and auditory inputs.

Oscillatory Entrainment of Primary Somatosensory Cortex Encodes Visual Control of Tactile Processing

“…Several thalamic regions have been reported to react to stimulation of more than one sensory modality, representing possible relay stations of cross-modal effects . Simultaneous visual and tactile stimulation activated neurons in the medial geniculate body (Wepsic, 1966) and reticular nucleus (Sugitani, 1979). Similarly, cross-modal interactions have been reported for the auditory thalamus (Komura et al, 2005).…”

Axonal regeneration from GABAergic neurons in the adult rat thalamus

“…Anatomic studies with retrograde and anterograde tracers showed that the neurons of the RNT receive topographicallyorganized collateral inputs from both the thalamo-cortical and the cortico-thalamic projections (Jones, 1975). Although the Golgi preparations (Scheibel & Scheibel, 1966) suggested that some RNT axons ramify widely throughout the thalamus, more recent electrophysiologic and anatomic studies indicate that neurons in particular regions of the RNT tend to project to the nearby parts of the thalamus (Hale et al, 1982;Sugitani, 1979;Montero, 1983) where they presumably act as inhibitory modulators (for review, see Jones, 1981). Further evidence for an inhibitory role for the RNT was provided by the demonstration that RNT neurons react immunocytochemically for glutamic acid decarboxylase (GAD), the major enzyme involved in the synthesis of gamma-aminobutyric acid (GABA) (Houser et al, 1980;Oertel et al, 1983;Ohara et aI., 1983).…”

Projection and innervation patterns of individual thalamic reticular axons in the thalamus of the adult rat: A three-dimensional, graphic, and morphometric analysis

“…Anatomical and physiological studies have shown that Rt cells are scattered throughout the Rt into sectors according to the modality of the sensory inputs (Montero et al, 1977;Pollin and Rokyta, 1982;Shosaku, 1985;Shosaku et al, 1984;Sugitani, 1979). Every sector (visual, somatosensory, auditory, motor, or limbic) receives axon collaterals from reciprocally connected thalamic nuclei and cortical areas and projects back only to the corresponding thalamic nuclei (Bourassa et al, 1995;Bourassa and Deschênes, 1995;Fitzgibbon, 1994;Fitzgibbon et al, 1995;Hale et al, 1982;Harris, 1987;Jones, 1975;Minderhood, 1971;Ramon y Cajal, 1909-11;Scheibel and Scheibel, 1966;Steriade et al, 1984;Tai et al, 1995;Van Groen and Wyss, 1995;Velayos et al, 1989).…”