Biomedical subjects

R W Hunsperger

Publications and source records attributed to R W Hunsperger.

4 recordsLinked to original sources

PubMed1979

An electronic device for generating drifting grating patterns alternating with diffuse illumination of equal mean luminosity.

An electronic device for generating contrast patterns on a display unit is described. The apparatus permits the generation of spatially periodic bright and dark stripes of 5 different spatial frequencies, any desired orientation, and drifting velocities from 0 to 16 c/sec. The pattern is shown either over the whole screen or inside a window which can be shifted to any desired position in the surrounding of equal mean luminosity. The graftings can be alternated with diffuse illumination of equal mean luminosity at repetition frequencies between 0.5 and 16 Hz, with independent control of the duration of the contrast pattern.

Lighting↗

PubMed1978

Threat, attack and flight elicited by electrical stimulation of the ventromedial hypothalamus of the marmoset monkey Callithrix jacchus.

In order to elucidate whether relatively primitive primates show a similar topological organization of substrates mediating defense and flight within the ventromedial hypothalamus as has been found in other mammals, 15 marmosets (Callithrix jacchus) were chronically implanted with a total of 57 electrodes for electrical stimulation. Experiments took place in a familiar environment and under systematically altered conditions. All anatomical sites yielding vocal threat and short attacks were found to be situated in the n. ventromedialis. Flight was elicited from a region immediately lateral to this nucleus and from sites in the posterior hypothalamus. Thus, it appears that the topological organization of defense and flight behavior in cat, oppossum and marmoset are essentially similar.

Aggression↗

PubMed1976

The integrative role of the intralaminar system of the thalamus in visual orientation and perception in the cat.

Electrical stimulation with repetitive pulses (6/sec) was applied to the internal medullary lamina and produced tonic contraversive turning movements of eyes and head which were associated with recruiting responses in the visual cortex. Optical gratings of a spatial frequency of 0.5 c/deg which alternated with diffuse illumination of equal intensity were then presented to the animal during conjugated adversive eye movements induced by intralaminar stimulation with continuous sine-wave alternating currents of 5000 c.p.s. The head of the animal was fixed except for rotation in the horizontal plane. Prior to intralaminar stimulation it was turned in the direction opposite to the induced eye movements so that the animal always viewed the central area of the screen. The potential recorded in the visual cortex in response to the gratings consisted of an initial positive-negative potential of the order of 20 muV followed by later deflections of irregular shape. The size of this initial potential was measured during induced gazing and in the absence of intralaminar stimulation. A significantly greater potential in response to the gratings was found during gazing. Diminishing the visual acuity of the animal resulted in a marked decrease of the initial potential and in this condition very little increase was obtained during gazing. No enhancement of the potential was seen when stimulation was applied to other thalamic structures that yielded no visual orientation. It is concluded that perception of contrast is improved during visual orientation and that the effect is due to a concomitant activation of unspecific intralaminar afferents to the visual cortex.

Animals↗

PubMed1975

Functional significance of projection from the cerebellar nuclei to the motor cortex in the cat.

The functional organization of projections from the cerebellar subcortical nuclei to the motor cortex through the nucleus ventralis lateralis (VL) of the thalamus was studied using tungsten microelectrodes for stimulation and recordings in acute and chronic cats. The following results were obtained. (1) Microstimulation of a small area of the ventral thalamus produced contraction of a single limb muscle as well as movements of whiskers. (2) The stimulus parameters for producing low threshold contraction of limb muscles were different from those for face muscles. The decrease of the frequency gradualy increased the threshold values for face muscles whereas the decrease abruptly increased the threshold for limb muscles. The optimum duration of the train for the lowest thresholds was longer for face muscles. (3) Stimulation of cerebellar nuclei (interpositus and lateralis) produced contraction of limb muscles. The stimulus parameters for the minimum threshold were similar to those for producing contraction of limb muscles from the ventral thalamus. (4) The peripheral receptive fields of neurons located around the low threshold sites in the thalamus were diffuse, i.e. they were driven insecurely by twisting the joints or pressure to the deep structures, but could not be driven by touch or light pressure on a circumscribed area of the body. (5) Chronic ablation of the motor cortex did not abolish the muscle contractions produced by thalamic stimulation, excluding the possibility that the effects were produced by stimulation of the branches of the pyramidal tract fibers reaching the ventral thalamus. (6) Chronic section of the brachium conjunctivum abolished or changed the characteristics of the contractions produced by thalamic stimulation indicating that the previous effects were produced by stimulation of cerebellar efferent fibers reaching the thalamus. (7) From these results it was concluded that the efferent impulses originating from the cerebellar nuclei can produce contraction of a particular muscle through activation of the red nucleus. These impulses are, at the same time, transmitted to a small group of neurons in the VL and then forwarded to the neurons in the motor cortex. (8) The functional significance of the VL projection system has been discussed in relation to the efferent zones within the motor cortex.

Animals↗