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Biomedical subjects

J Illes

Publications and source records attributed to J Illes.

14 recordsLinked to original sources
PubMed1990

Effects of prolonged mental work on functional brain topography.

Topographic patterns of event-related covariance between electrodes were measured from subjects performing a difficult memory and fine-motor control task for 10-14 h. Striking changes occurred in the patterns after subjects performed the task for an average of 7-9 h, but before performance deteriorated. Pattern strength was reduced in a fraction-of-a-second-long response preparation interval over midline precentral areas and over the entire left hemisphere. By contrast, pattern strength in a succeeding response inhibition interval was reduced over all areas. The pattern changed least in an intervening interval associated with visual-stimulus processing. This suggests that, in addition to the well-known global reduction in neuroelectric signal strength, functional neural networks are selectively affected by sustained mental work in specific fraction-of-a-second task intervals.

Analysis of Variance↗
PubMed1989

Neurolinguistic features of spontaneous language production dissociate three forms of neurodegenerative disease: Alzheimer's, Huntington's, and Parkinson's.

An analysis of the temporal (prospective) form (silent and filled hesitations, repetitions, incomplete phrases, context-related comments, interjections), syntactic form, and lexical (retrospective) form (verbal deviations, open and closed class phrases) of spontaneous language production of early and middle stage Alzheimer's, Huntington's, and Parkinson's patients was made. Results showed that the language structure was disrupted in each disease, but in different ways. Temporal interruptions of varying types were frequent in the language of Alzheimer's and Huntington's Disease patients; only long-duration silent hesitations were frequent in Parkinson's language samples. Syntactic complexity was reduced in Huntington's Disease. Verbal paraphasias were found in both the language of Alzheimer's patients, as well as moderately advanced Huntington's patients. Closed class phrases were predominant in the language of Alzheimer's patients and Huntington's patients, and open class phrases in the language of Parkinson's patients. Taken together, the results suggest that (1) there is a unique neurolinguistic profile for spontaneous language production for each neurodegenerative disease, (2) pathology of the neostriatum disrupts syntactic organization, (3) adaptive strategies are used to cope with verbal and speech-motor difficulties, and (4) adaptive strategies fail to be effective with increasing disease severity.

Adult↗
PubMed1988

Language production in Parkinson's disease: acoustic and linguistic considerations.

The hypokinetic dysarthria of Parkinson's disease (PD) has been described extensively. In contrast, patterns of hesitation and the language structure in spontaneous speech of the PD patient have not been investigated, although several studies have shown language-related abnormalities in word naming, word generation, and verbal recall. In the present study, 10 male Parkinson's patients and 10 normal male speakers were compared in a reading and spontaneous speaking paradigm for acoustic and linguistic features. Among acoustic measures, fundamental frequency and relative intensity differentiated PD from control subjects, consistent with reported features of hypokinetic dysarthria. The striking observations among linguistic measures differentiating PD from control subjects were an increase in the number of (a) silent hesitations per minute, (b) abnormally long silent hesitations, (c) words per silent hesitation, (d) open class phrases, and (e) optional open phrases per speech sample, and a decrease in the number of modalizations and interjections. An increase in the number of filled hesitations occurring per minute, as well as a decrease in syntactic complexity separated moderate from mild Parkinson's patients. Our interpretation of the data favors the hypothesis that changes in the structure of spontaneous language production with increasing severity of dysarthria reflect PD patients' adaptation to their disease.

Dysarthria↗
PubMed1987

Human neuroelectric patterns predict performance accuracy.

In seven right-handed adults, the brain electrical patterns before accurate performance differed from the patterns before inaccurate performance. Activity overlying the left frontal cortex and the motor and parietal cortices contralateral to the performing hand preceded accurate left- or right-hand performance. Additional strong activity overlying midline motor and premotor cortices preceded left-hand performance. These measurements suggest that brief, spatially distributed neural activity patterns, or "preparatory sets," in distinct cognitive, somesthetic-motor, and integrative motor areas of the human brain may be essential precursors of accurate visuomotor performance.

Adult↗
PubMed1987

Neurolinguistic characteristics of language production in Huntington's disease: a preliminary report.

Samples of spontaneous and descriptive speech were obtained from 12 patients with Huntington's disease (HD) and 24 at risk (AR) controls. The data were assessed according to a neurolinguistic protocol. HD was identified with a significant reduction in number of words produced, a diminished level of syntactic complexity, reductions of melodic line, phrase length, articulatory agility, and grammatical form, and increases in paraphasic errors and word-finding difficulty. The data were interpreted in support of the hypothesis that neostriatal pathology affects linguistic processing.

Aphasia↗
PubMed1986

Effects of 18-hydroxydeoxycorticosterone on central nervous system excitability.

The effects of 18-hydroxydeoxycorticosterone (18-OH-DOC) on central nervous system excitability were studied in adrenalectomized rats. Sixty-four evoked potentials (EP) recorded from the pontine reticular formation were averaged before and after the injection of vehicle and hormone. 750 micrograms of 18-OH-DOC dissolved in 0.5 ml of a 4:1 saline Cremophor-EL solution were injected i.v. A decrease of 55.7 +/- 6.1% in the amplitude of the EPs was observed with the hormone 16.3 min +/- 2.7 (SE) after injection. Amplitude values returned to baseline levels 38 min +/- 6.8 (SE) after injection. The secretion of 18-OH-DOC is greatly increased by ACTH and might modulate central nervous system function.

18-Hydroxydesoxycorticosterone↗
PubMed1985

Maturation of visual callosal connections in visually deprived kittens: a challenging critical period.

The number of callosally projecting neurons (callosal neurons) which can be labeled in cortical areas 17 and 18 by horseradish peroxidase (HRP), injected in the contralateral visual cortex, is reduced to about 50% of normal in cats reared with their eyelids bilaterally sutured. In the same animals the density of HRP anterogradely transported to areas 17 and 18 is also decreased. The apparent loss of callosal neurons is limited to layers III and IV (subzone a), whereas layer VI (subzone c) is unaffected. The effect is obtained after 3 months or more but not after 1 month of deprivation. Two months of visual experience following deprivation do not restitute a normal number of callosal neurons. However, 10 days of normal visual experience preceding the deprivation are sufficient to prevent the effects of the latter. Animals deprived of vision after a short period of normal visual experience and animals allowed normal vision after 1 month of visual deprivation have a more widespread distribution of callosal neurons than do normal animals; in this way they are similar to previously described cats reared with convergent or divergent strabismus, monocular enucleation, or monocular eyelid suture. The results suggest that: vision is actively responsible for both the maintenance and the elimination of fractions of the juvenile callosal connections; the elimination which normally takes place during the second postnatal month requires normal binocular vision; and activity-dependent competition between callosal and other axons can explain the role of vision.

Animals↗
PubMed1982

Role of ipsilateral forebrain in lateral hypothalamic stimulation reward in rats.

The forebrain was ablated unilaterally to a level dorsal to the thalamus and anterior commissure. Ipsilateral lateral hypothalamic electrodes were then implanted and the animal was tested for self-stimulation behavior. Tests included an initial test for behavioral reactivity to changes in reward level and then two estimates of the quantitative relationships between stimulation parameters: the number-current and charge-duration relationships. Comparison between these findings and those known for intact rats suggest that the substrate for unilateral hypothalamic stimulation reward is not impaired by removal of the ipsilateral tissue.

Animals↗
PubMedDate not supplied

Event-related covariances during a bimanual visuomotor task. II. Preparation and feedback.

Event-related covariance (ERC) patterns were computed from pre-stimulus and feedback intervals of a bimanual, visuomotor judgment task performed by 7 right-handed men. Late contingent negative variation (CNV) ERC patterns that preceded subsequently accurate right- or left-hand responses differed from patterns that preceded subsequently inaccurate responses. Recordings from electrodes placed at left frontal, midline antero-central, and appropriately contralateral central and parietal sites were prominent in ERC patterns of subsequently accurate performances. This suggests that a distributed cortical 'preparatory network,' composed of distinct cognitive, integrative motor, somesthetic, and motor components, is essential for accurate visuomotor performance. ERC patterns related to feedback about accurate and inaccurate responses were similar to each other in the interval immediately after feedback onset, but began to differ in an interval spanning an early P300 peak. The difference became even greater in an interval spanning a late P300 peak. For both early and late P300 peaks, ERC patterns following feedback about inaccurate performance involved more frontal sites than did those following feedback about accurate performance. Together with the stimulus- and response-locked results presented in part I, results of this study on the preparatory and feedback periods suggest that ERCs show salient features of the rapidly shifting, functional cortical networks that are responsible for simple cognitive tasks. ERCs thus provide a new perspective on information processing in the human brain in relation to behavior--a perspective that supplements conventional EEG and ERP procedures.

Adult↗
PubMedDate not supplied

Event-related covariances during a bimanual visuomotor task. I. Methods and analysis of stimulus- and response-locked data.

A new method that measures between-channel, event-related covariances (ERCs) from scalp-recorded brain signals has been developed. The method was applied to recordings of 26 EEG channels from 7 right-handed men performing a bimanual visuomotor judgment task that required fine motor control. Covariance and time-delay measures were derived from pairs of filtered, laplacian-derived, averaged wave forms, which were enhanced by rejection of outlying trials, in intervals spanning event-related potential components. Stimulus- and response-locked ERC patterns were consistent with functional neuroanatomical models of visual stimulus processing and response execution. In early post-stimulus intervals, ERC patterns differed according to the physical properties of the stimulus; in later intervals, the patterns differed according to the subjective interpretation of the stimulus. The response-locked ERC patterns suggested 4 major cortical generators for the voluntary fine motor control required by the task: motor, somesthetic, premotor and/or supplementary motor, and prefrontal. This new method may thus be an advancement toward characterizing, both spatially and temporally, functional cortical networks in the human brain responsible for perception and action.

Adult↗