Effects of foveal prestriate and inferotemporal lesions on visual discrimination by rhesus monkeys

Summary Ablation of inferotemporal cortex in monkeys impairs visual discrimination learning, and inferotemporal cortex receives visual information from striate cortex by way of the circumstriate belt. Yet most previous studies have failed to find any discrimination impairment after partial ablations of the circumstriate belt.In this experiment severe impairments in post-operative acquisition and retention of visual discrimination problems were found after lesions of foveal prestriate cortex, i.e. the portion of the circumstriate belt which receives a projection from the cortical representation of the fovea in striate cortex and which lies, largely buried, in the ventrolateral portion of prestriate cortex. Although foveal prestriate lesions produced a greater impairment on individual pattern discrimination tasks than inferotemporal lesions, the opposite was true of concurrent visual discrimination tasks in which several different pairs of discriminanda are presented in each testing session until the animal learns to discriminate every pair.The results are related to a two-stage model of discrimination learning and it is suggested that foveal prestriate lesions impair visual attention or perception, whereas inferotemporal lesions disturb the associative or mnemonic stage of visual discrimination learning.This work was supported by National Institute of Mental Health Grant MH-14471, National Science Foundation Grant GB-6999 and United Cerebral Palsy Research Grant R/213/67. For providing travel expenses to the United States A. Cowey wishes to thank the H.E. Durham Fund of King's College, Cambridge, and the Royal Society. The authors are particularly indebted to D.B. Bender for advice and technical assistance. We wish to thank Dr. Mortimer Mishkin for sharing with us his ideas, enthusiasm and unpublished data.The terminology for the subdivisions of the non-striate visual areas of the occipital and temporal lobes of the monkey is still rather confusing. This is hardly surprising, for the subdivision of these areas on cytoarchitectonic grounds by different authorities is contradictory and the study of the properties of single units in these areas has only begun. Although the recent demonstrations by Zeki (1969b) and Cragg and Ainsworth (1969) that lateral striate cortex has two topographic and a third non-topographic projection onto prestriate cortex is a major step forward, the exact boundaries of these projections and their detailed relations to the various cytoarchitectonic subdivisions and subdivisions based on electrophysiological data are not yet entirely clear. Since the terminology used in behavioural studies of lesions of the non-striate visual areas is also inconsistent, it may be helpful to explain the terminology we have used in this report.     

Interhemispheric transfer of visual learning in monkeys with intact optic chiasm

Summary The purpose of the present experiments was to investigate the role of the forebrain commissures in interhemispheric visual transfer when both eyes are open and the optic chiasm is intact. Cynomolgus monkeys (Macaca fascicularis) learned a series of two-choice simultaneous visual discriminations. The visual stimuli were bipartite, with independently determined left and right halves. If such a stimulus is fixated centrally, the two halves fall into opposite visual hemifields. After 10 trials of acquisition of each discrimination, the same discriminanda were presented for a further 10 trials in which, within each stimulus, the positions of the halves were exchanged: the left half became the right and vice versa. The unoperated animals transferred well to the altered stimuli, making many fewer errors than they made in learning the originally presented discrimination. In contrast, monkeys with section of the posterior corpus callosum and the anterior commissure transferred poorly. These effects show that the forebrain commissures are important for the interhemispheric transfer and integration of visual information in animals with a normal, intact peripheral visual system.     

The effect of ablation of frontal eye-fields and superior colliculi on visual stability and movement discrimination in rhesus monkeys

Summary The neurological basis of the maintenance of a stable visual scene by means of a corollary discharge mechanism was investigated. Monkeys were trained to detect and respond to sudden rapid movement of a small spot of light in an otherwise totally dark environment. There was no evidence that after removal of the frontal eye-fields, superior colliculi, or caudal superior temporal sulcus the animals confused real movement of the target with retinal image movement caused by changing the position of head and eyes. This result was confirmed by an examination of the ipsiversive turning that follows unilateral frontal eye-field or collicular ablation. If the turning is a compensation for apparent movement of the visual world when the eyes are moved it should not be present in total darkness. It was still present.The thresholds for the smallest detectable instantaneous displacement of the target were also measured. The threshold was impaired by bilateral superior colliculus lesions but not by removal of the frontal eye-fields or cortex of the caudal part of the superior temporal sulcus.Abbreviations A nucleus anterior - Br brachium of superior colliculus - Caud caudate nucleus - CC corpus callosum - CG central grey - CP cerebellar peduncles - Cs1 nucleus centralis lateralis superior - F fornix - IC inferior colliculus - LD nucleus lateralis dorsalis - LH lateral habenular nucleus - mc, mf, pc pars multicellularis, multiformis and parvocellularis, respectively, of the dorsomedial nucleus - MD nucleus medialis dorsalis - Pcn nucleus paracentralis - PT pretectal region - Pul pulvinar - SC superior colliculus - TN trochlear nerve - V nucleus ventralis     

Localization and detection of visual stimuli in monkeys with pulvinar lesions

Summary Since the pulvinar receives a major ascending projection of the superior colliculus, pulvinar lesions might produce behavioral impairments resembling those that follow colliculus lesions. To test this possibility, we examined the effect of pulvinar lesions in monkeys on the localization and detection of brief light flashes, a task in which monkeys with colliculus lesions are severely impaired. Some of the pulvinar-lesioned monkeys showed localization impairments similar to those in monkeys with colliculus lesions. However, histological analyses of the lesions suggested that these deficits were related not to the pulvinar damage per se, but rather to interruption of corticotectal fibers that pass through the pulvinar. We conclude that the pulvinar is not critical for the ability to locate and detect brief visual stimuli.Supported by research grants MH 26489 from the National Institute of Mental Health and EY02254 from the National Eye Institute     

Cortical responses to light in unanesthetized monkeys and their alteration by visual system lesions

Summary In unanesthetized rhesus monkeys, visual evoked responses were recorded and averaged from epidural electrodes over striate, prestriate, inferotemporal and frontal cortex before and after unilateral striate lesions, unilateral optic tract section and unilateral inferotemporal lesions. The early wavelets seen in the striate and prestriate responses were eliminated only by ipsilateral optic tract section or ipsilateral striate lesions. The slower components of the striate responses were drastically reduced by ipsilateral optic tract section. Contralateral optic tract section and striate ablation also reduced the amplitude of these components, but to a lesser extent. Whereas ipsilateral optic tract section markedly reduced the amplitude of the inferotemporal response, the most striking effect of ipsilateral striate ablation on this response was a reduction in its variability. The inferotemporal lesion had no effect on the striate responses. The results are related to the problems of visual input to cerebral cortex, the functions of the inferotemporal cortex and the effects of occipital damage in man.This research was begun in the Department of Psychology, Massachusetts Institute of Technology. It was supported by N.I.H. Grants MH-05673, MH-06723, MH-6418, HD-01907 and 1-K3-NB-31,816, N.S.F. Grants GB 4104 and GB 6999, N.A.S.A. Grant NsG-496 and grants to M.I.T. from the Hartford and Rockefeller Foundations. We thank Professor H.-L. xxTeuber for helpful discussions, Prof. W.J.H. xxNauta for performing the optic tract sections, Miss L. xxRolnitsky for computer programming, R.C. xxHull for experimental assistance and Mrs. C.E. xxThomson for preparation of the brain sections.     

Correlated neuronal variability in monkey visual cortex revealed by a multi-microelectrode

Summary Recordings from the visual cortex of anaesthetized monkeys taken with a 30-fold multimicroelectrode demonstrate that the neuronal variability, defined as the change in response strength over time spans of a few seconds to several minutes, is highly correlated within groups of neurones. Several such groups exhibiting independent variability between groups, coexist within the area recorded. This within-group covariance suggests that a major part of neuronal variability is due not to a noise process in the cells, but rather to additional inputs to the neurones, which are not under control of the experimenter.Supported by the Deutsche Forschungsgemeinschaft, Sonderforschungsbereich 70 Hirnforschung und Sinnesphysiologie     

Schedule-induced drinking following omission of reinforcement in the rhesus monkey

Schedule-induced drinking in rhesus monkeys was studied with a variable second-order schedule, which consisted of FI 1-min components with 80% of the intervals being randomly reinforced. Schedule-induced drinking was found to occur after delivery of a food pellet and, also, after presentation of a stimulus which had previously been paired with food delivery. It was concluded that schedule-induced drinking is not just simply a post-prandial behavior.     

Frontal eye field lesions in monkeys disrupt visual pursuit

Summary Discussions of the cortical control of eye movement have generally attributed the generation of saccadic movements to the frontal eye fields (FEF) and the control of pursuit movements to posterior parietal or prestriate cortex. Monkeys were trained to perform a series of oculomotor tasks, including both saccade and pursuit paradigms. Surgical ablation of the frontal eye fields produced only minor disruption of saccade performance, but caused a dramatic deficit in the ability of monkeys to visually track a slowly moving target. This disorder has not previously been associated with FEF lesions. These results necessitate a major re-evaluation of the way in which the cerebral cortex participates in oculomotor control.     

由视觉新奇刺激产生的P_3a的特点

目的：探讨与作业不相关的新奇性刺激于额-中央区产生的P3a的特性。方法：采用视觉具有新奇性刺激的oddball作业，记录了61名健康右利手小学生的事件相关电位（ERP）和Fz、Cz、Pz、C3、C4、P3、P4的脑电图以及左侧眼电图，分析了各导、各刺激平均ERP和脑电地形图分布。结果：正确检测靶刺激产生于Pz的P3b潜伏期较长（417-425ms）；峰幅值最高（22．7-23．9μV）；新奇性刺激于额-中央区产生最大的P3a，潜伏期比P3b短（402-416ms）。结论：新奇刺激产生的P3a有独立的特性和脑内起源。     

Neuronal activity in the dorsolateral pontine nucleus of the alert monkey modulated by visual stimuli and eye movements

Summary The activity of neurons in the dorsolateral pontine nucleus (dlpn) was studied in two awake rhesus monkeys trained to participate in a variety of visual and oculomotor tests. The visual and eye movement related responses of 73 neurons encountered in the more caudal part of the dlpn were analyzed. Thirty eight of these could be assigned to one of the three following groups. Visual-only neurons (Type 1, n = 10) responded to movement of a broad range of visual stimuli in certain preferred directions. Their receptive fields were usually large, not restricted to the contralateral visual field and always included the fovea. Visual-tracking (VT) neurons (n = 28) discharged in relation to smooth pursuit of a small target in particular preferred directions. Nine of these (Type 2) did not respond to visual stimulation during stationary fixation. Nineteen VT-cells (Type 3) discharged in relation to both visual tracking and visual stimulation. In 9 of the Type 3 neurons, the preferred directions for visual stimulation and tracking were opposite, whereas they were the same in the other 10. Visual responses of Type 3 neurons were indistinguishable from those of Type 1 neurons. Testing of an additional 9 neurons driven by either visual-tracking or pattern movement was not sufficient to allow a definite assignment to one of the groups 1, 2 or 3. The distribution of preferred directions for both visual stimulation and visual tracking was widely scattered between 0 and 360 deg. Our results suggest that the dlpn is a constituent in a cerebro-cerebellar loop important for the generation of smooth pursuit eye movements.     

In-vitro protein evolution by ribosome display and mRNA display

In-vitro display technologies combine two important advantages for identifying and optimizing ligands by evolutionary strategies. First, by obviating the need to transform cells in order to generate and select libraries, they allow a much higher library diversity. Second, by including PCR as an integral step in the procedure, they make PCR-based mutagenesis strategies convenient. The resulting iteration between diversification and selection allows true Darwinian protein evolution to occur in vitro.

We describe two such selection methods, ribosome display and mRNA display. In ribosome display, the translated protein remains connected to the ribosome and to its encoding mRNA; the resulting ternary complex is used for selection. In mRNA display, mRNA is first translated and then covalently bonded to the protein it encodes, using puromycin as an adaptor molecule. The covalent mRNA–protein adduct is purified from the ribosome and used for selection. Successful examples of high-affinity, specific target-binding molecules selected by in-vitro display methods include peptides, antibodies, enzymes, and engineered scaffolds, such as fibronectin type III domains and synthetic ankyrins, which can mimic antibody function.     

基于生理信息的视频显示终端精神疲劳状态研究

为寻找诊断与评测视频显示终端(VDT)精神疲劳状态的客观指标,设计VDT精神疲劳实验,实时采集被试者的体温信号和心电(ECG)信号。通过对被试者体温信号时域和ECG信号时域、频域的分析,提取人体温度、心率(HR)和心率变异性(HRV)作为精神疲劳的评测客观参量。被试者在精神疲劳实验后,体温显著升高(P<0.001),RR-PNN50明显升高(P<0.05),ECG信号的S波明显下降(P<0.05);自然恢复后与精神疲劳测试实验结束时相比,体温升高,RR-PNN50变化不明显,S波显著升高(P<0.01),精神疲劳程度有所缓解。实验结果表明,通过对体温信号和ECG信号的分析有望找到评测VDT精神疲劳的客观指标。     

Selection of visual targets activates prelunate cortical cells in trained rhesus monkey

Summary Cells in monkey prelunate association cortex display an enhanced visual activity after the onset of a stimulus in the receptive field, when the stimulus is simultaneously selected as a target for a saccadic eye movement. In the present study we observed a separate activation which is independent of the passive visual on-response and occurs in a given cell when the animal saccades to a steady stimulus in its receptive field. The activation begins when the stimulus is selected for foveation before the eye actually moves, but is not necessarily predictive for an eye movement.This work was supported by the Sonderforschungsbereich Hirnforschung und Sinnesphysiologie (SFB 70/Tp B7)     

Rotatable raster generator for visual research

This paper presents a design for generating a raster on a general purpose X-Y-Z oscilloscope display which may be rotated to any angle and held, or may be set into smooth rotation in a clockwise or counter-clockwise direction allowing visual stimuli to be presented at any angle. The resolution and frame rate are limited by the oscilloscope display, and are typically 700 lines at a refresh rate of 125 Hz.     

Organization of the cerebellar tongue representation in the monkey

Summary The cerebellar nuclei of rhesus monkeys were stimulated electrically and evoked responses of the tongue recorded with force-displacement transducers and electromyographically. Stimulation of the dentate (DN) and fastigial (FN) nuclei produced different effects on the tongue musculature, the former evoking movements characterized by changes in both the lateral and anteroposterior (AP) dimensions of the tongue and the latter movements associated with a preferential change in the AP dimension. While all three deep nuclei influenced the genioglossus muscle, the influences varied across nuclei in the following manner: FN produced the largest amplitude genioglossus mediated AP excursions and DN the smallest, with the nucleus interpositus (NI) occupying an intermediate position; and, FN and medial NI stimulation evoked changes in genioglossus respiratory activity whereas DN stimulation did not. These data indicate that the cerebellar tongue representation is organized into different functional zones and that within an anatomically broad representation of a single target muscle, nuclear functional specificity exists.     

Subcortical projections of the dorsomedial visual Area (DM) of visual association cortex in the owl monkey,aotus trivirgatus

Summary The efferent subcortical connections of the dorsomedial cortical visual area (DM) in the owl monkey were determined by tracing degenerating axons following lesions or by tracing axonal pathways following injection of radioactively labeled proline. Areas of termination included structures which are known to receive input from many other regions of cortex such as the claustrum, putamen, caudate nucleus, reticular nucleus of the thalamus and pontine nuclei. Other terminations were in subcortical structures which primarily receive input from visual areas: these included the pregeniculate nucleus, the medial and central divisions of the inferior pulvinar nucleus, two loci in the superior pulvinar complex, the pretectum and the superior colliculus. Terminations were also seen in the lateral posterior nucleus, a part of the thalamus associated with the somatosensory system. These results further identify Area DM as an integral part of the visual system, suggest functional subdivisions of the pulvinar complex, and implicate the lateral posterior nucleus in the mediation of visual, as well as somatosensory, behavior.Supported by NIH Grant NS 12377, NSF Grant GB 36779, and NIH Training Grant MH-08107     

Serotonin-immunoreactivity in the monkey lateral geniculate nucleus

Summary Serotonin-immunoreactivity in the monkey lateral geniculate nucleus appears as a plexus of fine, beaded fibers decreasing in density from magnocellular to parvocellular laminae. Ultrastructurally, these fibers show strictures and dilations, and are filled with dense round particles as well as granular material attached to outer mitochondrial membranes and microtubules. Most of the profiles followed in serial sections lack morphologically defined synapses. The few synapses observed are asymmetric, some with subjunctional dense bodies. This appearance suggests a possible excitatory effect mainly on interneurons which in turn would inhibit principal cells. Serotonin released non-synaptically may block the delivery of transmitters from retinal terminals and/or the receptors for such transmitters, thereby exerting a modulatory depressing action on principal cells.     

Electrophysiological correlates of visual perceptual masking in monkeys

Summary Monkeys were trained to discriminate with nearly 100% accuracy between a square and a triangle presented simultaneously in a brief tachistoscopic flash. Perceptual masking was demonstrated by inability to perform this trained visual discrimination at better than chance level when the information flash was followed in less than 20 msec by a blank second flash. In order to determine the nature and locus of this retroactive visual perceptual masking effect, electrical potentials were recorded simultaneously from three points along the optic pathways: optic nerve or tract, lateral geniculate body, and visual cortex. Potentials were computer-averaged and correlated with the monkey's ability or inability to make a correct behavioral response to the information contained in the first or test flash (T). When the perception of T was masked by the second or blanking flash (B), only the evoked potential characteristic of B was observed at all recording sites, including the optic nerve or tract. This suggested that the interaction underlying masking occurred in the retina since optic nerve or tract responses are dependent upon retinal ganglion cells. When T was not masked, an early portion of the evoked response to T could be detected at all recording sites. Perception of T was possible when only the initial segment of the T-potential (15 msec or less) was present at each recording site. Thus the visual information transfer essential to the performance of an already learned visual discrimination task appears to occur very early in the course of the evoked response and is not dependent upon later or secondary components.Supported by grants from the Office of Naval Research (Nonr-4756) and National Aeronautics and Space Administration (NASA NGL 05-007-049). Aided by National Institute of Mental Health Training Grant 5 TI MH-6415.     

Visual cortex ablation and thresholds for successively presented stimuli in rhesus monkeys: II. Hue

Summary Rhesus monkeys were trained to discriminate successively presented hues. The smallest difference they could reliably detect was determined before and after either inferotemporal ablation, or a lesion intended to remove as much as possible of prestriate area V4 (Zeki, 1973).As a group, the animals with lesions of V4 showed good but not perfect retention of their preoperative performance, and their thresholds were unaltered. The inferotemporal group showed no retention of the simplest successive task, red versus green, but after relearning their thresholds too were unaltered. It appears that animals without inferotemporal cortex can form precise internal representations of hues, and that the basis of the inferotemporal learning impairment may depend upon the nature of the stimuli to be discriminated.     

Prism adaptation with delayed visual error signals in the monkey

Errors in reaching produced by displacing the visual field with wedge prisms decrease with trials, even when the error is not revealed until the completion of the movement. To examine how much additional delay in visual feed-back the monkey can compensate for, the effects of delaying the visual error signals were studied by presenting the terminal visual images after one of five delays, ranging from 0 to 500 ms. Adaptation was fastest when the delay was 0 or 10 ms, decreased significantly with a delay as small as 50 ms and approached zero when the delay was 500 ms. The size of the after-effect decreased with the delay accordingly. The results indicate that prism adaptation in the monkey critically depends on the availability of visual information within 50 ms of completion of the movement. Comparing the results with those for humans, we suggest that monkey and human share a mechanism of adaptation with a short time window of 50 ms, but the monkey lacks another mechanism of adaptation that allows a visual delay of 500 ms or more in humans.