Kenzo Konishi

Attention-related negative brain potential for speech words and pure tones

Abstract Event-related potentials (ERPs) were recorded during performance of a selective attention task in which speech words and pure tones were dichotically delivered at random. To estimate the attention-related negative shift, ERPs to unattended stimuli were subtracted from ERPs to attended stimuli. The difference waves for both non-target words and tones demonstrated a biphasic wave form: a fronto-centrally distributed component with a peak latency at about 165 msec and a more frontally focussed component which peaked about 300 msec. The scalp distributions, differential experimental manipulations and developing time-courses suggest that the early negativity manifests the auditory discrimination activity on a task-relevant stimulus for deciding whether it is a target or not, whereas the late negativity reflects modality-nonspecific activation processes which may be associated with ‘momentary effort’ or ‘orienting’ triggered by detection of the task relevancy. Neither the early nor late components, however, presented hemispheric asymmetry corresponding to linguistic processing.

P300 and Reaction Time in Parkinson's Disease

The event-related potential and motor reaction time were simultaneously recorded in 35 patients with Parkinsons disease (26 nondemented and nine demented) and 15 age-matched neurologically normal control subjects during the performance of visual discrimination tasks. There were no significant differences in either the latency or amplitude of the P300 component between the nondemented patients and the control subjects, but the patients with nondemented Parkinsons disease had a significantly prolonged reaction time compared with the controls. In patients with demented Parkinsons disease, both P300 latency and reaction time were significantly prolonged compared with the normal controls. These results suggest that response selection and execution are impaired in patients with nondemented Parkinsons disease, although the stimulus evaluation process is largely preserved, whereas patients with demented Parkinsons disease have impairment of stimulus evaluation, go/no-go response selection, and execution.

Computed tomographic findings in relation to event-related potentials during visual discrimination tasks in patients with multiple cerebral infarcts

Event-related potentials were recorded for 29 patients with multiple cerebral infarcts (MCI) (mean age, 65.7 years) during visual discrimination tasks to clarify the relationship between computed tomographic findings (CT) and P300 component. P300 latency in patients with MCI was significantly longer than that of 15 age-matched normal subjects (mean age, 65.4 years), although no significant difference was found in P300 amplitude between the two groups. There was a significant negative correlation between P300 latency and mental status as determined by the Hasegawas Dementia Scale. Significant correlation was also found between P300 latency and the degree of ventricular dilatation or severity of periventricular lucency (PVL) on CT scan. P300 latency was not significantly correlated with the number of infarcts. P300 latency in patients with MCI thus appears related to the severity of PVLs and degree of ventricular dilatation in addition to mental status.

CEREBRAL BLOOD FLOW AND EVENT-RELATED POTENTIAL IN PATIENTS WITH MULTIPLE CEREBRAL INFARCTS

Cerebral blood flow and P300, a long-latency, positive component of the scalp-recorded, event-related potential (ERP), were measured in 26 patients with multiple cerebral infarcts (mean age, 65.0 years). Compared with age-matched normal subjects, patients with multiple cerebral infarcts had significantly lower cortical blood flow values and had prolongation of the P300 latency. There was a significant correlation between the P300 latency and the mean cortical blood flow values in patients with multiple cerebral infarcts. These results suggest that, in patients with multiple cerebral infarcts, the cognitive impairment associated with change of the ERP may be related to reduction of cortical blood flow.