Thus, in the currently used tasks, behavioural slowing is produced by stages later than response selection. Specifically, the contralateral MRPs were substantially enhanced and prolonged in aged individuals in the CRT, whereas the ipsilateral motor activity did not differentiate the two age groups in the CRT. Previous results from the visual modality have not presented unambiguous conclusions about the origin of sensorimotor slowing with ageing.
When different dimensions of visual stimuli had to be selected, neither sensory discrimination, as indexed by ERP components, nor response initiation, as reflected by LRP onsets, were affected by ageing Kenemans et al. Kok, ; Curran et al.
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The critical question to be raised is whether this deficient motor activation in the older subjects is caused by a neurobiological alteration of the underlying substrate per se Raz, , or does it result from a functional dysregulation of the motor cortex Sailer et al. A negative MRP component with characteristics similar to those observed in the present study has been consistently correlated with functional activation of the primary motor area during voluntary movement Kristeva et al.
One possible explanation of this finding is that the excitability of cortical motor neurons is reduced with age.
Sensorimotor Impairment in the Elderly | George E. Stelmach | Springer
Previous cellular studies on animals Mednikova and Kopytova, and transcranial magnetic stimulation in humans Rossini et al. However, a basic reduction of motor cortex excitability should affect each type of response in the older adults, irrespective of whether the response is produced in a simple or in a complex task.
This observation indicates that age effects on MRP originate from functional rather than basic substrate deficiencies. From a functional point of view, neuronal excitability can vary according to the amount of ongoing subthreshold activation. In sensorimotor tasks, a functional facilitation depolarization of the motor cortex may occur to promote a faster effective stage of response production Rockstroh, ; Brunia, ; Brunia and van Boxtel, Given that the amplitude of the MRP peak virtually measures the difference between the electrical activity before and during the movement, the findings of smaller and shorter MRPs in the SRT relative to the CRT are consistent with this explanation.
Another consequence is that the threshold of effective response production can be reached faster, as also found for the SRT. Hence, these task effects on MRP magnitude and duration can be explained with a functional modulation of the reactivity of the contralateral motor cortex. Notably, a functional dysregulation of the motor cortex in older subjects could be noticed even in the SRT, as demonstrated by differences in the functional involvement of ipsilateral motor regions in this condition.
These findings show that a functional dysregulation of the motor cortex activations is present in older subjects even in the absence of behavioural deficits.
Yet, in the simple task, alterations in the ipsilateral activations do not seem to influence behaviour, whereas in the more complex task, the effective contralateral motor cortex is involved, which is accompanied by response delay. Indeed, the present results additionally indicate that the functional dysregulation affecting the motor cortex in aged individuals appears to expand and affect other processing systems in the CRT. This is evinced by the results from the early P1 component.
In the SRT, no differences were detected in the amplitudes of the P1 component between young and older adults. In this regard, it may be also suggested that when older adults perform a more complex sensorimotor task, their motor responses need to be guided by or executed with a stronger reference to external stimuli, so that more attention is focused on these stimuli to support movement execution. Considering all these results together, several conclusions can be proposed about the functional origins of sensorimotor slowing with increasing age.
In contrast to previous EEG and neuroimageing studies, the currently employed advanced ERP methodology enhanced the spatial characteristics and quantified the timing of neural events from the millisecond scale.
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As a result, a functional dysregulation of the contralateral motor cortex made a major contribution to delayed RTs in aged individuals. The onset of motor response potentials MRP is marked with an arrow. Positivity up calibration units are not shown because the figure is schematic. Topography maps of grand average potentials left and group mean values right of peak P1 amplitudes in young and older subjects for the a auditory and b visual modality. Data from three recording sessions are pooled.
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Postural Imbalance in the Elderly: Main Aspects
Google Scholar. Vasil Kolev. Joachim Hohnsbein. Michael Falkenstein. Cite Citation. Permissions Icon Permissions. Open in new tab Download slide. Table 1. Open in new tab.
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Table 2. Alain C, Woods DL. Psychol Aging. Allison T. Development and aging changes in humans evoked potentials. In: Barber C, Blum T, editors. Evoked potentials III. Boston: Butherworths; Amenedo E, Diaz F. Biol Psychol.
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Effects of aging on visuospatial attention: an ERP study. Use of partial stimulus information in response processing. Exp Brain Res. Cognitive neuroscience: the biology of the mind. New York: WW Norton; J Clin Neurophysiol. In the following sections, an overview of the ACTIVE study is presented, followed by a description of the present study sample, procedures, measures, and proposed statistical analyses for exploring sensorimotor cognitive associations.
The interventions consisted of training in memory, reasoning, or speed of processing, all of which are empirically supported for improving their targeted cognitive ability. Briefly, assessment of cognitive functioning was conducted at baseline, 1 month post training, and at 1, 2, 3, 5, and 10 years post initial training.