1990

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Lack of age effects on human brain potentials preceding voluntary movements

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Authors:

  • Jaswinder Singh

  • Robert T. Knight

  • David L. Woods

  • Dennis J. Beckley

  • Clay Clayworth

Date: 1990

PubMed: 2097580

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Abstract:

We examined age effects on Movement related potentials (MRPs) in 13 young (mean age = 29.3 years) and 13 old (mean age = 67.2 years) normal adults in right, left and bimanual self-paced button press conditions. Both the groups generated a slowly rising readiness potential (RP) at about 1000 ms, a negative shift (NS') at about 450 ms and a motor potential (MP) at about 100 ms prior to movement. The RP was symmetrical, bilaterally distributed and maximal at the vertex in all conditions in both the groups. Both the groups produced contralateraUy enhanced NS' and MP compo- nents in unimanual conditions. In contrast to prior reports, topographical distribution, onset latency and mean amplitude were comparable between young and old subjects for the RP, NS' and MP components of the MRP. The results indicate that motor programming as indexed by MRPs is unaffected by normal aging.

Frontal lobe contribution to voluntary movements in humans

Authors:

  • Jaswinder Singh

  • Robert T. Knight

Date: 1990

PubMed: 2289137

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Abstract:

We assessed the contribution of human prefrontal cortex to movement related potentials (MRPs) generated prior to voluntary movements. MRPs were recorded during self-paced movements of the right thumb (experimental condition I), the left thumb (experimental condition II) and both thumbs (experimental condition III) from patients with focal lesions centered in dorsolateral frontal association cortex (PFCx, n = 11) and in age matched controls (n = 11). Controls generated a slowly rising readiness potential (RP) beginning at about 1000 ms prior to movement. A negative shift (NS') began at about 450 ms and a motor potential (MP) appeared at about 100 ms prior to movement. Both the NS' and MP were maximal over scalp sites contralateral to movements. Unilateral PFCx lesions preferentially reduced the RP and NS' components of the MRP. This indicates that PFCx is involved in a neural network beginning at least 1000 ms prior to movement. The differential PFCx effects on the early (RP, NS') and late components (MP) suggest that these MRPs index different movement-related circuits.

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Evoked potential mapping of auditory and somatosensory cortices in the miniature swine

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Authors:

  • R. J. Andrews

  • Robert T. Knight

  • Randall P. Kirby

Date: 1990

PubMed: 2116608

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Abstract:

The miniature swine (Sus scrofa) is a desirable model for certain electrophysiological studies because of its large brain, ready availability and low cost. We report our findings regarding the location of the auditory and somatosensory cortices obtained by cortical surface evoked potential mapping. Data were collected from 11 animals under general endotracheal anesthesia. Consistent positive potentials were obtained for both auditory (P24) and median nerve somatosensory (P26) stimulation. The auditory region was centered around the lateral (sylvian) fissure; the somatosensory region was centered around the central (dorsomedial suprasylvian) fissure. In the miniature swine the locations of the auditory and somatosensory cortices are comparable to those found in other species.

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Gating of somatosensory input by human prefrontal cortex

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Authors:

  • Shuhei Yamaguchi

  • Robert T. Knight

Date: 1990

PubMed: 2207666

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Abstract:

Somatosensory evoked potentials (SEPs) to median nerve stimulation were recorded in controls and in patients with focal lesions in dorsolateral prefrontal cortex (PFCx). Unilateral PFCx lesions increased the amplitude of the P26 component generated in postcentral areas 1 and 2. The amplitudes of the N28, P45 and N67 SEP components recorded over post-rolandic and frontal electrodes were also enhanced by PFCx damage. In contrast, the N19 component generated in postcentral area 3b was unaffected by PFCx lesions. The results indicate that PFCx exerts inhibitory modulation on sensory processing that may be mediated by corticocortical PFCx-parietal connections.

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Movement related potentials in patients with MPTP-induced Parkinsonism and early and late Parkinsonism

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Authors:

  • Jaswinder Singh

  • B. R. Bloem

  • Robert T. Knight

  • William Jagust

  • David L. Woods

  • Dennis J. Beckley

  • J. Tetrud

  • J. W. Langston

Date: 1990

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Component Mechanisms Underlying the Processing of Hierarchically Organized Patterns: Inferences From Patients With Unilateral Cortical Lesions

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Authors:

  • Michele Lazzara

  • Lynn C. Robertson

  • Robert T. Knight

Date: 1990

PubMed: 2140405

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Abstract:

Subjects identified target letters that occurred randomly at the local or global level in a divided attention task. The visual angle of the stimuli was varied. Neurologically intact controls showed a reaction time advantage for local targets which increased as visual angle increased. Patients with lesions centered in the posterior superior temporal gyms (STG) showed a larger local advantage than controls if the lesion was on the right and a global advantage if the lesion was on the left. STG patients were no more influenced by visual angle than were controls. Control subjects also showed the usual interference of global distractors on responding to local targets. STG patients showed little evidence of interference. Control patients with lesions centered in the rostral inferior parietal lobe performed normally. The findings suggest that several component mechanisms are involved in the processing of hierarchical levels of structure, each linked to specific anatomical regions.