Showing papers in "Journal of Neurophysiology in 1972"

Visual properties of neurons in inferotemporal cortex of the Macaque.

Abstract: IN THE LAST DEC,ADE, considerable progress has been made in understanding the physiology of one of the most fundamental aspects of human experience: perception of the visual world. It is now clear that the retina and visual pathways do not simply transmit a mosaic of Iight and dark to some central sensorium. Rather, even at the retinal level, specific features of visual stimuli are detected and their presence communicated to the next level. In cats and monkeys, the geniculostriate visual system consists of a series of converging and diverging connections such that at each successive tier of processing mechanism, single neurons respond to increasingly more specific visual stimuli falling on an increasingly wider area of the retina (19-Z). How far does this analytical-synthetic process continue whereby individual cells have more and more specific trigger features? Are there regions of the brain beyond striate and prestriatel cortex where this processing of visual information is carrie,d further? If so, how far and in what way? Are there cells that are concerned with the storage of visual information as well as its analysis? There are several lines of evidence suggesting that a possible site for further processing of visual information and perhaps even for storage of such information might, in the monkey, be inferotemporal cortexthe cortex on the inferior convexity of the temporal lobe. First, this area receives afferents from prestriate cortex which itself processes visual information received from

Single-unit recording and stimulation in superior colliculus of the alert rhesus monkey.

Abstract: RECENT SINGLE-UNIT recording studies of the alert rhesus monkey superior colliculus have disclosed that the deeper layers of this structure contain cells which discharge in association with eye movement (15-17, 23, 24). Such units fire selectively prior to saccades of a specific direction and size, irrespective of the position of the eye in orbit. Stimulation studies of the superior colliculus have so far produced conflicting results. Some reports suggest that in the alert cat stimulation brings the eye to a certain position in orbit irrespective of eye position prior to stimulation (1, 9, 19). Thus, the size and direction of elicited saccades is reported to vary as a function of initial eye position. By contrast, in the alert monkey it has recently been reported that stimulation produces conjugate saccades of a specific size and direction; these parameters are the same no matter where the eye is in the orbit prior to stimulation (12, 15, 16). The stimulation map of Robinson (12) shows a reasonable correspondence with the receptive-field map of the superior colliculus reported by Cynader and Berman (5). The aim of this study was to clarify the relationship between recording and stimulation data by using methods which allow a direct comparison. We used alert rhesus monkeys which had one eye immobilized for the mapping of visual receptive fields. The other eye was normal, thus permitting the study of eye movement. Stimulation and recording were carried out using the same low-resistance microelectrode; for each site sampled, records were obtained for both single-unit activity and for electrical stimulation.

Receptive-field organization of monkey superior colliculus.

Abstract: A NUMBER OF recent studies suggest that the mammalian superior colliculus plays a crucial role in visually guided behavior (33, 35). Ablation experiments indicate that lesions in the hamster superior colliculus can cause severe deficits in orienting to visual and auditory stimuli while leaving intact the ability to discriminate pat serns in situ .ations in whi ch no orienting component is necessary for the successful performance of the discrimination (32). Related to this view is the idea that the colliculus plays an important role in the control of eye and head movements. After unilateral colliculectomy in the monkey, Denny-Brown (6) reports a fascinating cluster of eye-movement deficits. While the animal could look to either side or up and down, there was a slight divergent strabismus, and the optokinetic response was present only when the stripes entered the visual field from the operated side. Though the monkey could reach accurately for an object in the visual field contralateral to the lesion, he could not fixate the object, but only looked in its general direction. After bilateral colliculus lesions, monkeys showed fixed gaze, lack of reactivity to visual stimuli; lack of vocalization, and a variety of other deficits which led Denny-Brown to describe this structure as the “pattern setter of the nervous system.” Though other workers have failed to confirm the oculomotor deficits reported in this study (2, 28), recent work usi *g more sophisticated methods for head immobilization and eyemovement recording has confirmed and extended many of Denny-Brown’s original observations (M. Stryker, P. H. Schiller, and F. Koerner, unpublished observations). It

Learning Centers of Rat Brain Mapped by Measuring Latencies of Conditioned Unit Responses

Abstract: THE QUESTION OF whether certain parts of the brain play an especially important role in processes related to learning and memory has been pursued by a variety of methods with limited success. Lesion studies (1.3) suggested that if “engrams” resided in cortex, they were not localized to particular parts of it; nevertheless, newer studies (18) indicated that particul ar parts of the subcortical sys tern (posterior thalam us, for example) might w fashion ,ell

Relay of receptive-field properties in dorsal lateral geniculate nucleus of the cat.

Abstract: THE DORSAL lateral geniculate nucleus (LGNd) of the cat is a principal relay nucleus on the direct pathway from the retina to the visual cortex, and several parameters of its organization as a relay are well established. First, relay cells of the LGNd have either onor off-center receptive fields (16), because each relay cell receives direct excitatory drive from either onor off-center retinal ganglion cells (6, 16). Second, retinal ganglion cells fall into two groups (X-cells and Y-cells) according to whether they sum the influences of the center and surround regions of their receptive fields linearly or nonlinearly (8). Most LGNd relay cells can be similarly classified because most receive direct excitatory drive from either Xor Y-type retinal ganglion cells (6). Third, each relay cell receives direct excitatory drive from either fastor slow-conducting retinal afferents, and its own axon is correspondingly either fast or slow conducting (6, 36). The two latter parameters are closely correlated since Y-cells have been shown to have fast axons and Xcells, slow axons (6, 11). The on/off organization is independent of the other two parameters, however. Roth Y-cells and Xcells can have either onor off-center fields. This report examines several features of the LGNd relay in the normal cat, extending previous concepts and establishing a spectrum of normal properties against which the properties of the LGNd in deprived cats (described in the following paper (3W can be compared. First, the separate relay in the LGNd of the Xand Y-cell activity of the retina is described. Second, several properties of Xand Y-cells of the LGNd were observed to vary con-

Loss of a specific cell type from dorsal lateral geniculate nucleus in visually deprived cats.

Abstract: cATs REARED under various conditions of visual deprivation are deficient in their subsequent performance of certain visual tasks (6, 19). Wiesel and Hubel (15-17, 25-28) have sought the physiological basis of these effects by comparing receptivefield properties of single visual neurons of normhlly reared cats to those of visually deprived cats. Their consistent finding (17, 26-28), confirmed by others (7), is that cells of the striate cortex develop permanently abnormal receptive-field properties during deprivation rearing. In a preliminary study, Wiesel and Hubel (25) observed that cells of the dorsal lateral geniculate nucleus (LGNd) in visually deprived cats have essentially normal receptive fields despite the loss of many large cells in this nucleus. These findings have been subtantially confirmed (11, 24). The present studv which follows note the a series presence of of t recent wo funct papers ionallv distinct types of cell in the cat’s retina and LGNd: the X-cells (3, 13) (type II (5, 21) or sustained cells (2)) and the Y-cells (3, 13) (type I (5, 21) or transient cells (2)). This paper presents evidence that one effect of rearing cats with visual deprivation (achieved by neonatal eyelid suture) is the selective elimination from the LGNd of Y-cells. The remaining neurons appear to be functionally normal.

Crayfish escape behavior and central synapses. I. Neural circuit exciting lateral giant fiber.

Abstract: CRAYFISH ARE SOUGHT as food by fish, birds, amphibia, and mammals, as well as man (54, p. 460). They commonly escape these predators by darting backward and away from an enemy on contact, or as the predator approaches. This maneuver is accomplished by a sudden flexion of the tail, exerting a thrust backward and sometimes upward against the aquatic medium. A single tail flexion, commonly called a tail flip or flick, often suffices; a more prolonged mode of escape, swimming, consists of a periodic sequence of abdominal flexions and extensions. In 1947, Wiersma (67) showed that stimulation of any single lateral or medial giant fiber of the nerve cord lecl to a ra&l abclominal flexion. Recently it has been shown that the giant fibers excite all of the fast flexor motoneurons of the abdomen which innervate the phasic flexor muscles (37, 38, 61). It has been assumed from this evidence that the giant fibers are the sole command or decision fibers responsible for eliciting escape behavior. Schrameck (60) has shown, however, that many tail flicks-including most of those in swimming-are accompanied by giant fiber spikes in intact, unrestrainecl, chronically implanted animals. Nevertheless, recent experiments by Wine and Krasne (71) show that a phasic mechanical stimulus to the tail leads to tail flicks that are always mediatecl by lateral giant fiber activity. For this particular input, therefore, the lateral giant is a critical decision fiber for the behavior. Krasne has also found that repetition of the stimulus as slowly as once per minute reveals a lability in the response, which fails to follow an increasing proportion of the stimuli. The be-

Crayfish escape behavior and central synapses. II. Physiological mechanisms underlying behavioral habituation.

Abstract: responsible for exciting the lateral giant neuron and initiating single tail flips in response to phasic mechanical stimuli to the tail of crayfish. It was shown that the excitation of some tactile interneurons by tactile afferents antifacilitates extensively at low repetition rates. This phenomenon must be presumed to contribute to the habituation of the response. It is not clear, however, that this is the only phenomenon responsible for generating lability in the behavior. Receptor fatigue, variable properties of the excitable membranes of the lateral giant or the tactile interneurons, or labile properties of the circuit efferent to the giant are additional possibilities. One other point of lability has in fact been found. The strength of transmission at the neuromuscular junction between the motor giant neuron and the phasic flexor muscles is very sensitive to stimuli recurring only once per minute; this junction rapidly ceases to transmit activity after only a few stimuli (6). The motor giant is sometimes excited by the lateral giant (20, 39), and so it appears that this is a source of declining response strength in the efferent limb of the neural circuit mediating escape. However, this loss of transmission is adequately compensated by the continued activation of several nongiant flexor motoneurons, whose neuromuscular junctions facilitate (33, 39). Furthermore, electrical stimulation of the lateral giant axon at frequencies up to 5 Hz can elicit up to 50 apparently normal tail flips (unpublished observations; see also ref

Relations among climbing fiber responses of nearby Purkinje Cells.

Abstract: ACIWITY PATTERNS in the cerebellar cortex may be studied by simultaneously recording from two or more cells whose spatial separation and orientation are known Appropriate statistics such as the cross-correlogram may then be used to describe the temporal relationships Further computational and experimental methods some times permit an interpretation of the temporal relationships in terms of the underlying anatomical connections (20, 23, 24) Two quite different types of discharges may be recorded from cerebellar Purkinje cells, simple spikes and complex spikes Simple spikes are similar to nerve impulses recorded elsewhere in the central nervous system and are evoked primarily through parallel fiber activation Complex spikes have the same sharp initial component, but this is followed by a slow wave lasting 10-15 msec on which ripples or small spikes are superimposed The complex spike has been shown to be the response of the Purkinje cell to a single spike or a brief burst of spikes in the climbing fiber axon (11), and is also referred to as a climbing fiber response (CFR) In our previous work (6) we found that the simple spikes of nearby Purkinje cells were often correlated in time It was suggested that the temporal relationship between two such discharges depended on the parallel fiber input shared by the two cells and consequently could be related rather precisely to their spatial separation and orientation on the cerebellar sheet Freeman (14) has made the same suggestion and provided experimental support for it The present experiments also used the method of statistically analyzing simultaneous recordings from two or more cells