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PubMed2005

The influence of movement cues on intermanual interactions.

In two experiments, we studied intermanual interactions in bimanual reversal movements and bimanual aiming movements. Targets were presented on a monitor or directly on the table on which the movements were produced. Amplitudes for each hand were cued symbolically or spatially either in advance of an imperative signal or simultaneous with it. In contrast to findings of Diedrichsen et al. (Psychological Science, 12, 493-498, 2001), reaction times for different-amplitude movements were longer than for same-amplitude movements both for symbolic and spatial cues presented on the monitor and directly on the table. However, with symbolic cues the effect of the relation between target amplitudes was considerably stronger than with spatial cues, no matter where the cues were presented. Intermanual correlations of amplitudes, movement times, and reaction times were smaller with different than with same target amplitudes, and this modulation was more pronounced when targets and cues were presented on the monitor than when they were presented on the table. The findings are taken to suggest that the basic reaction-time disadvantage of different-amplitude movements results from interference between concurrent processes of amplitude specification. Additional factors like interference between concurrent processes of mapping cues on movement characteristics may add strongly to it.

Adolescent↗
PubMed2007

Executive function in preschoolers with autism: evidence consistent with a secondary deficit.

Recent research on executive function (EF) deficits in autism has led investigators to conclude that EF deficits are secondary to the disorder. The current study has two major goals: (1) Examine whether specific EF deficits are present in the youngest autism group to date (mean=2.9 years), and (2) examine whether such deficits are secondary to autism, or act as an early non-specific cognitive risk factor for autism by comparing EF abilities of this autism group to a CA-matched typically developing group. Results from Experiment 1 suggest no specific EF deficits in autism relative to MA-matched controls, while results from Experiment 2 are consistent with the hypothesis that EF deficits may emerge as a secondary deficit in autism. Alternative hypotheses are also considered.

Aptitude↗
PubMed1992

Topographical changes in alpha power in medicated and unmedicated schizophrenics during digits span reverse matching test.

The topographical distribution of alpha power reduction was compared in nine unmedicated schizophrenics (predominantly never-treated), 17 medicated schizophrenics, and 15 normal controls. The task involved four procedures: (1) listening to signal sound, (2) listening to digits for memorization, (3) after listening, and (4) listening to digits for recognition. The electroencephalograms (EEGs) during each procedure were analyzed with Fast Fourier Transformation and compared with EEGs at rest. While listening to the digits, medicated schizophrenics showed less alpha power reduction than normal controls and unmedicated schizophrenics. In addition, there were correlations found between the degree of alpha power reduction and medication dose, and score of chronic symptoms. These suggest that patients with different clinical backgrounds have differing cerebral activity.

Adult↗
PubMed1980

The effect of lesions of the dorsal cap of the inferior olive on the vestibulo-ocular and optokinetic systems of the cat.

The gain (eye velocity/head velocity) of the vestibulo-ocular reflex (VOR) of cats was measured in the dark and light for sinusoidal head oscillations at 0.05 and 1.2 Hz with peak velocity of about 30 deg/sec. Animals wore visual reversing prisms chronically and were also subjected to forced oscillation in the light at 0.05 Hz for 2 h per day. Such experience produced adaptive reduction in VOR gain in the dark from 0.85 to 0.10 within about 4 days; qualitatively similar effects were observed at 1.2 Hz. In 4 cats, the dorsal cap of the inferior olive was located electrophysiologically by its responses to visual motion, and bilateral electrolytic lesions were made in or near this structure. The location of lesions was subsequently identified by histology. After lesions, 3 cats were unable to make adaptive changes in VOR gain when confronted with the same reversing prism paradigm; the fourth exhibited appreciable retardation of adaptation. These results imply that the dorsal cap is essential for plastic adaptation of the VOR. However, all cats retained the ability to use reversed vision to reduce VOR gain in the light after lesions. Optokinetic nystagmus (OKN) and optokinetic after nystagmus (OKAN) were measured in a striped optokinetic drum, before and after dorsal cap lesions, at drum velocities of 20 and 40 deg/sec. Lesions of the dorsal cap in 4 cats did not impair either OKN or OKAN. This result indicates that the climbing fiber system reaching the flocculus from the inferior olive is not essential for such optokinetic movements.

Animals↗
PubMed1986

Corticosteroid receptor plasticity and recovery of a deficient hippocampus-associated behavior after unilateral (dorsal) hippocampectomy.

Unilateral ablation of the right dorsal hippocampus (HCX) produced changes in maximal corticosteroid binding capacity (Bmax) in the contralateral hippocampal lobe of the rat with time. The mechanism by which this time course of changes was produced seemed to involve the pituitary-adrenal system, since a certain difference in corticosteroid receptor binding pattern was noted between chronic adrenalectomized (ADX) rats and rats which remained intact during postlesion survival. In the presence of endogenous adrenal hormones the HCX-induced changes in corticosteroid receptor binding relative to that observed in rats with the overlying neocortex ablated (control) were the following: a 26% decrease at 5 days after HCX; an increase the following 3 weeks with a maximum of 46% at 20 days postsurgery; and recovery towards control values after longer survival times. After discrimination of corticosteroid binding into two corticosterone (CORT) binding receptor populations, e.g. glucocorticoid receptors (GR) and mineralocorticoid-like or CORT receptors (CR), the lesion-induced effect was more pronounced in GR than in CR. A 72% increase over controls was measured at 20 days postsurgery. In the absence of the adrenals, however, the Bmax of corticosteroid binding was not decreased at 5 days after HCX. The relative increase in Bmax reached a maximum of 39% over control levels at 30 days postsurgery and recovery towards control values after longer survival did not occur. The increase in corticosteroid receptor capacity after HCX, therefore, is transient in the presence of adrenocortical secretion and permanent in its absence.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenalectomy↗
PubMed1993

Reserpine impairs spatial working memory performance in monkeys: reversal by the alpha 2-adrenergic agonist clonidine.

Repeated daily treatment with the catecholamine-depleting agent, reserpine, dramatically reduced performance on the delayed response task, a test of spatial working memory that depends upon the integrity of the prefrontal cortex. Delayed response performance fell from an average of 27.2/30 trials correct before reserpine treatment to an average of 20.4/30 trials correct after repeated reserpine administration. Injection of the alpha 2-adrenergic agonist, clonidine (0.0001-0.05 mg/kg), to chronic reserpine-treated monkeys significantly restored performance on the delayed response task; performance after an optimal dose averaged 27.8/30 trials correct. Clonidine's beneficial effects on delayed response performance were longlasting; monkeys remained improved for more than 24 h after a single clonidine injection. The finding that clonidine is efficacious in reserpinized animals supports the hypothesis that alpha 2-adrenergic agonists improve cognitive function through actions at postsynaptic, alpha 2-adrenergic receptors on non-adrenergic cells. In contrast to the delayed response task, reserpine had little effect on performance of a visual discrimination task, a reference memory task which does not depend on the prefrontal cortex. These results emphasize the importance of postsynaptic, alpha 2-adrenergic mechanisms in the regulation of working memory.

Adrenergic alpha-Agonists↗
PubMed1992

Antidepressant profile in rodents of SR 58611A, a new selective agonist for atypical beta-adrenoceptors.

beta 2-Adrenoceptor agonists possess antidepressant-like activity in animals and man, but their peripheral side-effects prevent their therapeutic use. Atypical beta-adrenoceptors have not been demonstrated in the central nervous system, but are known to exist in peripheral tissues such as the rat colon. We have now studied the antidepressant-like effects in rodents of a new selective atypical beta-adrenoceptor agonist, SR 58611A. SR 58611A was active with minimal effective doses of 0.1-0.3 mg kg-1 i.p. in several models (antagonism of the hypothermia induced by apomorphine and reserpine; potentiation of the toxicity produced by yohimbine; reversal of learned helplessness), but was inactive in the tests of reserpine-induced ptosis and behavioural despair. The antidepressant-like effect of SR 58611A was not antagonised by selective beta 1- or beta 2-adrenoceptor antagonists, but was blocked by high doses of the non-selective beta-adrenoceptor antagonists, propranolol and alprenolol. Unlike beta 2-adrenoceptor agonists, SR 58611A did not reduce locomotor activity or increase water intake at doses up to 10 mg kg-1. Therefore, SR 58611A may represent the prototype of a new class of antidepressant compounds.

Adrenergic beta-Agonists↗
PubMed1980

Stimulation of a soluble protein fraction in the hippocampus of rats, subjected to brief training.

After a brief training period (2 x 25 min) consisting of reversal of handedness, soluble protein synthesis in the hippocampus was measured by incorporation of [3H]leucine and double labelling with [3H]valine and [14C]valine together with densitometric tracings of polyacrylamide gels. Among the proteins showing increased incorporation values, 3 polypeptides of mol. wt. 13,000, 30,000 and 65,000 were found. Thus, the soluble protein-polypeptide pattern in the hippocampus was found to be altered after a short training period for the establishment of a new behavior.

Animals↗
PubMed1982

Tricyclic antidepressant drug action correlates with its tissue levels in anterior neocortex.

In the behavioral reversal of learned helplessness in the rat by imipramine, a strong correlation is found between "cure" of helplessness and drug level in anterior neocortex, the locus of drug action in this model of depression. This suggests that the delayed onset of therapeutic action of antidepressant drugs is due to the time required to achieve adequate drug levels at the site of their action.

Animals↗
PubMed1982

Comparative neuropsychology and Korsakoff's syndrome. III--Delayed response, delayed alternation and DRL performance.

Performance of alcoholic Korsakoff patients was compared with that of patients with Huntington's disease. Broca's aphasia or alcoholism (without clinical signs of memory impairment) on delayed alternation (DA) and delayed response (DR) tests. Korsakoffs were impaired on both tasks, and Huntington patients were impaired on DA only. In a separate experiment, performance by Korsakoffs was compared to that of alcoholic and normal controls on four DRL schedules. Korsakoffs tended to be overresponsive, making errors of commission early within a schedule, and consequently, obtaining fewer reinforcements than the controls.

Adult↗
PubMed1989

Guidance of visual reaching with the aid of a TV monitor: the effects of monitor position and of left/right and up/down reversals of the image in relation to age.

Children, aged 2-9 years, were seated alongside a wall containing an opening through which they could reach with their preferred hand. Targets ("ink blots"), which could not be felt, were attached to the other (rear) side of the wall, around the opening. The child could see directly neither the target nor its hand beyond the front side of the wall; but both were visible on a TV monitor. The image on the screen of the monitor originated from a camera viewing the rear (target) side of the wall at the level of the central opening. The monitor screen was either (a) parallel to the wall, but rotated 180 degrees with respect to the axis of the camera, i.e. facing the camera; or (b) at 90 degrees to the wall; or (c) in a position similar to (a) but visible in a mirror attached to the front side of the wall and therefore in effect "aligned" with the axis of the camera. The image the child saw was either (1) electronically unswitched, i.e. when the target was towards the east on the wall it was to the west on the monitor in monitor position (a), or to the north in position (b), or to the "east" in position (c); or (2) left/right reversed relative to (1); or (3) up/down reversed relative to (1); or (4) both left/right and up/down reversed. The dependent variable was the time taken for the child to place the palm of the hand over the target (time was measured to 0.1 sec on video-recorder with a superimposed time display). Position of the monitor, comparing conditions (a)-(c), gave only minor, perhaps age-related, effects. Left/right reversals were easier than up/down reversals under monitor positions (a) and (b), but not under (c); but both reversals could be achieved by age 3 or older; hardest was condition (4). However, with monitor positions (a) and (b) children, at all ages we tested, found condition (1) ("east gives west/north") easier than (2) ("east gives east/south"), whereas for adults these conditions were equally easy, or they found (2) easier than (1); but with monitor position (c) condition (1), now "east gives east", was easiest. Moreover, the claim that chimpanzees but not monkeys can achieve accurate reaching under the conditions varied in this study seems premature: the chimpanzees may have made use of strategies based on uncontrolled cues.

Attention↗
PubMed1990

Impaired verbal reasoning and constructional apraxia in subjects with right hemisphere damage.

In addition to causing visuospatial deficits, damage to the right cerebral hemisphere also impairs other cognitive abilities, including those requiring higher-order aspects of language. The present study used a standardized test battery to examine the relationship between visuospatial abilities and comprehension of narrative material in subjects having unilateral right hemisphere damage (RHD). In a series of 41 consecutively admitted RHD subjects, impairments in abstracting information from narrative passages were as prevalent and as severe in magnitude as constructional apraxia. Moreover, the extent of the visuospatial and linguistic impairments were highly correlated. Although age, educational levels, and degree of premorbid brain atrophy were all found to influence performance, analysis of a select subgroup of the population established that the covariation of visuospatial and verbal impairments is related to right hemisphere damage per se. Clinically, these findings may be of significance for understanding the pervasive cognitive impairments that are often evidenced by RHD patients.

Aged↗