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J M Fuster

Publications and source records attributed to J M Fuster.

At least 55 records · Page 3Linked to original sources
PubMed1988

Prefrontal representation of stimulus attributes during delay tasks. II. The role of behavioral significance.

Rhesus monkeys were trained to perform two visual discrimination tasks with delayed response. In both tasks, the response depended on the color of the cue, a lighted circle in the center of a panel. Red and green guided one task, yellow and blue the other. In the course of performance, a fifth color (violet), non-relevant and inconsequential, was presented at random in the same location as the cues. All 5 stimuli were of equal brightness. Many cells in the dorsolateral prefrontal cortex (sulcus principalis and superior convexity) treated the relevant cues differently than the irrelevant stimulus. In general, cellular reactions to that stimulus were of lesser magnitude than the reactions to the cues. Cell reaction differences as a function of stimulus significance outnumbered and overshadowed differences as a function of cue-color or any other task variable. The results indicate that, during visual delay tasks, units in the dorsolateral prefrontal cortex differentiate stimuli by their behavioral significance, as well as by other stimulus attributes, including color. Because the motivational evaluation of sensory stimuli is an integral part of the cognitive processes in delay tasks (together with short-term memory and motor set), these results support the notion that the prefrontal cortex integrates motivational inputs into the structure of behavioral action.

Animals↗
PubMed1986

[Idiopathic diffuse polyalgia syndrome].

The term "idiopathic diffuse polyalgia syndrome" is suggested to designate an entity well known to neurologists, rheumatologists and all physicians interested in pain. In this syndrome pain is diffuse but often predominates in a given region. Physical examination shows excessive tenderness in well-defined areas. Radiological and laboratory examinations are negative. Psychological factors are not always obvious. Several arguments are in favour of dysfunction of the pain control mechanisms. The effectiveness of the various treatments prescribed is related to the quality of the doctor-patient relation.

Humans↗
PubMed1986

A microelectrode for depth recording in awake animals.

The manufacture is described of a metal, glass-coated microelectrode for single-cell recording from deep structures of the brain during behavioral testing. It is thin, long, and straight, and has excellent electrical properties.

Animals↗
PubMed1985

Functional interactions between inferotemporal and prefrontal cortex in a cognitive task.

Monkeys were trained to perform a visual short-term memory task (delayed matching to sample). In some of the animals, cooling probes were implanted over dorsolateral prefrontal cortex, covering sulcus principalis and adjacent areas; microelectrode pedestals were implanted over inferotemporal cortex. Other animals were fitted with converse implants: cooling probes over a portion of the inferotemporal cortical convexity and microelectrode pedestals over prefrontal cortex. In the awake and behaving monkeys, bilateral cooling of either the prefrontal or the inferotemporal region (to 20 degrees C) induced, in the other region, reversible changes of spontaneous and task-related cell discharge. In the two cortices remote cooling induced augmentations and diminutions of cell reaction to the color samples which the animal had to retain for correct performance of the task. The same was true for cell discharge during the delay, the retention period which followed each sample. However, a net effect of remote cooling was, in both cortices, a diminution of color-dependent differences in the reactions and delay-discharge of some cells. Concomitantly, errors of task-performance increased. Cells that as a result of remote cortical cooling showed changes of reaction to the color samples were found more commonly in supragranular than infragranular layers. The results are interpreted as evidence of mutual influences between inferotemporal and prefrontal areas, probably mediated by corticocortical connections. The single-cell data, together with the behavioral data, suggest that those influences are functionally important for visual discrimination and short-term memory.

Action Potentials↗
PubMed1985

Occipital and inferotemporal responses to visual signals in the monkey.

This study analyzes cellular and field-potential responses in striate and inferotemporal cortex to visual stimuli in monkeys performing a memory task (delayed matching-to-sample). Each trial was initiated by a brief alerting diffuse flash preceding presentation of the memorandum (sample); the latter was a lighted circle (red or green, 1.5 s) to be retained by the animal during a subsequent delay for correct behavioral response (color match). The alerting flash evoked distinct excitatory cell responses and field potentials in the occipital cortex; those two orders of phenomena were broadly related to each other in temporal terms. By contrast, most cells in the inferotemporal region were inhibited by the flash, although the local evoked field potential had a configuration similar to that of the occipital potential. In each region, the sample stimuli elicited excitatory unit responses which summed to a unimodal distribution with an initial component roughly corresponding in time course to the local field potential. Although the shortest response latencies were found in occipital cortex, considerable temporal overlap of the sample-related activities in the two cortices was observed. The finding that most inferotemporal cells, unlike occipital cells, treated only the sample with excitatory response indicates that the inferotemporal cortex is selectively attuned to visual detail. However, the largely simultaneous activation of both cortical regions following the onset of the sample suggests that discriminative visual information is processed by hierarchic interactions of the two cortices through their reciprocal connections.

Animals↗
PubMed1985

The elgiloy microelectrode: fabrication techniques and characteristics.

A glass-insulated microelectrode made from elgiloy orthodontic wire, a stainless cobalt-chromium alloy containing 15% iron, was described by Suzuki and Azuma (1976). Here, we detail a set of modified electrode fabrication procedures, including techniques for hardening and etching the wire, specifying the size, geometry and exposure of the tip, and adjusting tip impedance over a wide range. Accurate insulation of the tip with molten solder glass produces microelectrodes suitable for extracellular recording from single or multiple units and simultaneous recording of evoked potentials. The finished electrode is tough enough to withstand multiple penetrations of the thickened, fibrous dura of the chronic monkey preparation. The iron content allows Prussian blue staining of marking lesions for histological verification of recording sites.

Alloys↗
PubMed1985

The prefrontal cortex, mediator of cross-temporal contingencies.

A large body of empirical evidence supports the notion of a critical role of the prefrontal cortex in the temporal organization of goal-directed behavioral sequences. The key element of that role is the bridging of cross-temporal contingencies of behavior, in other words, the adjustment of the actions of the organism to temporally distant events and objectives. By the analysis of lesion effects, neuroelectrical phenomena, and metabolic activity we are led to conclude that the prefrontal cortex subserves at least three cognitive functions that allow the mediation of cross-temporal contingencies and, thereby, the formation of temporally extended structures of behavior: short-term memory, preparatory set, and control of interference. The three have a somewhat different topographic representation within the prefrontal cortex and thus the principle of its functional heterogeneity is upheld. However, all three sustain the supraordinate role of the prefrontal cortex in the temporal integration of behavior.

Animals↗
PubMed1982

Effects of ethanol on visual evoked responses in monkeys performing a memory task.

The effects of ethanol on behavior and visual evoked potentials were investigated in monkeys performing a visual short-term memory task. Ethanol induced a dose-dependent deficit in performance and a prolongation of visuo-motor reaction time. The normal patterns of ocular motility were concomitantly altered. The potentials elicited in the lateral geniculate nucleus, the striate cortex, the inferotemporal cortex, the amygdala, and the mesencephalic reticular formation by a colored stimulus used by the animal in the task were attenuated by the alcohol in dose-related manner. In contrast, potentials elicited in the striate cortex and reticular formation by a brief and diffuse flash were augmented under the influence of the substance. It is inferred that ethanol can increase the reactivity of reticular and cortical structures to undifferentiated stimuli, while at the same time interfering with the basic mechanisms of visual attention and perception.

Animals↗
PubMed1982

Principal component analysis of evoked responses and the effects of alcohol on the geniculo-striate system of the monkey.

This study was designed to test the effects of alcohol on visual evoked potentials in nonhuman primates performing a cognitive task. Flash evoked potentials were recorded from monkeys involved in a delayed matching-to-sample (DMS) paradigm in which the flash served as an alerting signal before each trial. Event-related potentials were recorded from the lateral geniculate nucleus and homolateral striate cortex before, during, and after intravenous administration of saline or ethanol (0.25, 0.5, 1.0, and 2.0 g/kg). Average evoked potentials (AEPs) were computed. Residual waveforms were obtained by subtracting the predrug AEP from postdrug AEPs. A principal component analysis was employed to define the alcohol alterations on the evoked responses. In the analysis each AEP was represented by 40 time points spaced 12 msec apart. These reduced representations of the AEP were entered in the variance-covariance matrix calculations. The first five eigenvectors were computed and plotted. Alcohol produced the greatest variance in the AEPs at the two highest dose levels. So the data were grouped together into three experimental categories: saline, low-dose (0.25-0.5 g/kg) and high-dose (1.0-2.0 g/kg). A correlation template, representing each category, was computed by correlating individual eigenvectors with each sequential average composed of 10 individual evoked potentials in the 200 trials of an experimental session. Alcohol affected the state vector from the brain by loading the correlation coefficient in the opposite direction following alcohol administration in two principal components. One or two of the eigenvectors significantly (P less than 0.01) shifted in geniculate nucleus, indicating that either the nucleus or a previous station was affected by alcohol. In comparison, three or more eigenvectors from striate cortex were shifted significantly following alcohol injection. This difference may be explained by the effect of alcohol on multisynaptic brain structures, including the brain-stem reticular formation, which in turn influenced the cortex.

Animals↗
PubMed1982

Neuronal firing in the inferotemporal cortex of the monkey in a visual memory task.

The objective of this study was to elucidate the functional role of neurons in the inferotemporal cortex of the primate. Single unit activity was recorded with microelectrodes in monkeys performing a visual delayed matching-to-sample task. On each trial, the animal was exposed briefly to a color - the sample - and, after a period of delay, had to select the same color among two or four colors simultaneously presented. Thus, correct performance of the task required perception, retention, and recognition of the sample color for every trial. A large number of inferotemporal units were seen to react to the stimuli with changes of firing frequency. Many units showed color-dependent reactions, suggesting their involvement in perception and discrimination of colors. A substantial contingent of cells showed increased, sustained, and in some cases, color-dependent discharge during the delay which was not necessarily preceded or succeeded by firing changes in sample or match periods. It is proposed that those cells were engaged in temporary retention of the sample stimulus. Since most of the inferotemporal units examined showed firing changes in more than one period of a trial, they appeared to be involved in more than one of the operations required by the task. Thus, the data do not support a clear-cut topographic separation of visual functions within the inferotmeporal cortex. However, neurons that appear to participate in visual memory, either exclusively or in addition to other functions, are concentrated in the cortex of the lower banks of the superior temporal sulcus.

Animals↗
PubMed1981

Inferotemporal neurons distinguish and retain behaviorally relevant features of visual stimuli.

Single-cell activity was recorded in the inferotemporal cortex of monkeys performing a task that requires perception and temporary retention of colored stimuli. Many cells reacted differentially to the stimuli. By changing the relevance of certain features of compound stimuli, it was found that the reactions of some cells to color depend critically on whether or not the task demands that the animal pay attention to color. A substantial number of cells showed color-dependent differences in frequency of discharge during the retention periods of the task. The temporal characteristics of differential discharge and its dissolution when memory is no longer required indicate that the cells that display it are involved in retaining visual information.

Action Potentials↗
PubMed1981

Single cell activity in ventral prefrontal cortex of behaving monkeys.

Single unit activity was recorded extracellularly from ventral prefrontal cortex (VPC) of monkeys during performance of two short-term memory tasks: spatial delayed response and delayed matching to sample. The tasks required perception, retention and recognition of visual cues differing in either color or spatial location. Two separate areas of VPC were explored: a lateral area in the lower prefrontal convexity and a medial area around the medial orbital sulcus. Two categories of unit activity were distinguished on the basis of frequency changes to the cue. One was characterized by non-specific discharge independent upon which cue was presented, the other by discriminative discharge related not only to visual qualities of the cue but to the animal's subsequent use of it. Nearly one-half of all units showed altered firing during the retention (delay) period as compared with intertrial control firing. Eighteen per cent displayed delay activity related to the quality of the preceding cue. The lateral and medial segments of VPC were not distinguished by differences of unit activity in cue or delay periods. Post-trial activity was related to presence or absence of reward. Type I cells showed firing changes following choice reinforcement as well as gratuitous reward; some showed changes in opposite direction following unreinforced choices. They may encode the availability of reward. Type II cells showed changes of activity after unreinforced trials and, in some cases, opposite changes after unexpected reward; they were not affected by the reward of normal correct-choice trials. These cells appear to react to deviations from expectancy of reward. Type III cells exhibited comparable firing changes following reinforced and unreinforced choices. They may encode termination of a trial sequence. Type I was more common in lateral than medial VPC, whereas the opposite was true for type II; type III did not clearly predominant in either area. Ablation studies have shown that the two areas of VPC differ in behavioral functions. This study of their cellular properties revealed topographic differences only during the post-trial period. It is therefore possible that the combination of cue and delay activity (related to exteroceptive input) with post-trial activity (related to interoceptive input) constitutes the neuronal basis for the two areas' differences in behavioral function.

Animals↗
PubMed1981

[Acute mercury vapour poisoning (author's transl)].

Two persons, exposed to high concentration of mercury vapour in their home developed a few hours later febrile illness with interstitial pneumonitis and mercurial stomatitis. Symptomatic treatment was associated with dimercaprol (BAL) and steroïds; an alveolar washing was performed to remove non-absorbed mercury in the respiratory three which seems to be responsible for the observed inflammatory reaction and, sometimes, the delayed development of fibrosis. A review of the literature revealed that such intoxications had been previously described in about 20 cases. Prognosis depends on the severity of the pulmonary lesions. Fatalities have been described in 9 cases (10%); in 8 cases the victims were young children or old people. An acute gingivo-stomatitis is generally observed. The onset of mercurial encephalopathy is an uncommon feature. Renal disturbances are exceptionally described and always mild. There is no correlation between the clinical condition of the patient and the levels of mercury in the urine.

Adult↗
PubMed1979

Woodpecker drilling behavior. An endorsement of the rotational theory of impact brain injury.

High-speed cinematograph films of a drilling woodpecker were examined by direct visual inspection and by a microdensitometer and computer-imaging technique. These showed (1) that the drilling trajectory is essentially linear, with very little, if any, rotation of the head; (2) that there is minimal movement after impact; (3) that the impact velocity is of the order of 600 to 700 cm/s; and (4) that the impact deceleration is of the order of 1,000 g. Dynamic and morphologic findings in the woodpecker may be highly relevant to the prevention of concussion and brain injury in man. Taken in the context of modern packaging technology and other animal and mathematical modelling research, they suggest that brain injury preventive systems could be greatly improved over those now in common use.

Animals↗