Biomedical subjects

S J Weate

Publications and source records attributed to S J Weate.

7 recordsLinked to original sources

PubMed1997

Contingent negative variation in epilepsy.

The contingent negative variation (CNV) is a long-latency event-related potential elicited by paired or associated stimuli. We recorded contingent negative variation in 50 patients with complex partial and secondarily generalized seizures and in 20 neurologically and psychiatrically normal unmedicated controls. CNV was recorded from Fz, Cz, and Pz. A 2000 Hz tone was followed after 1.5 s by 1000 microseconds light flash, at which a button press was to be executed. Filter band pass was 0.1-20 Hz, analysis time was 10 s and 10 responses were replicated. Patients with complex partial seizures with and without secondary generalization had lower measurements of area under the CNV curve (AUC) than did controls, and CNV amplitude was significantly reduced. Patients with interictal behavioural symptoms had significantly smaller AUC and lower amplitude. No significant difference was found between depressed and non-depressed seizure patients with respect to AUC, but amplitude was significantly lower in depressed patients. Seizure patients with psychosis had significantly lower AUC but did not differ from non-psychotic patients in CNV amplitude. No differences were found between seizure patients with and without personality disorder with respect to CNV AUC or amplitude. Post-imperative negative variation was significantly more common in seizure patients than in controls and among patients with epilepsy, was significantly increased in those with inter-ictal behaviour disturbance generally and psychosis particularly. No specific effect of anticonvulsant monotherapy on AUC or amplitude was identified. These findings suggest that CNV may differ between partial epilepsy patients and controls, and that inter-ictal behaviour disturbance may particularly affect CNV measures. They also agree with previous evidence for a frontal lobe generator for the CNV, and a possible role for central dopaminergic pathways in the production of PINV.

Adult↗

PubMed1996

Middle latency auditory evoked potentials in epilepsy.

Middle latency auditory evoked potentials (MLAEPs) have been recorded after cortical lesions and seizure surgery. We recorded interictal MLAEPs in 14 patients with well documented complex partial and secondary generalized seizures. Na and Pa potentials did not differ in latency between patients and controls, although both were longer among seizure patients. Pa and Na were significantly reduced in amplitude in complex partial seizure patients compared to controls. These findings accord with previous suggestions that MLAEPs may be generated subcortically but modulated by temporal lobe structures. MLAEPs may be of value in differentiating temporal and extratemporal epilepsy. They may also help clarify interictal cognitive or behavioral symptoms related to epilepsy or the effects of antiepileptic medication.

Adolescent↗

PubMed1996

Event-related potentials in Parkinson's disease.

The increasingly recognized occurrence of dementia in Parkinson's disease (PD) has prompted study of cognitive evoked potentials in this disorder. The P300 wave is related to cognitive performance, while the contingent negative variation (CNV) may reflect dopaminergic function. We measured P300 and CNV in 21 nondemented PD patients and compared them to elderly controls. The P300 was recorded from Cz with linked ear reference. 3,000 and 1,000 Hz tones were presented in an 80:20 ratio at 76 dBSL interstimulus interval was 1.1 seconds, and filter bandpass was 1-100 Hz. CNV recording utilized a 2000 Hz tone followed after 1.5 seconds by a light flash and button press, and was recorded from Fz with linked ear reference, 10-second analysis time, and 0.1-20 Hz filter bond pass. N200 and P300 amplitudes were significantly longer and latency significantly lower in PD patients than in controls, and P300 latency was correlated with composite score on cognitive tests. CNV amplitude was significantly reduced in PD patients, but was correlated with measures of motor disability rather than cognition. These findings suggest that bradyphrenia may occur in nondemented PD patients, and that P300 may measure cognitive changes in PD. CNV may be a dopaminergic slow potential and may correlate with motor function in nondemented PD patients.

Aged↗

PubMed1996

Auditory evoked potentials in postconcussive syndrome.

The neuropsychiatric sequelae of minor head trauma have been the source of controversy. Most clinical and imaging studies have shown no alteration after concussion, but neuropsychological and neuropathological abnormalities have been reported. Some changes in neurophysiologic diagnostic tests have been described in postconcussive syndrome. We recorded middle latency auditory evoked potentials (MLR) and slow vertex responses (SVR) in 20 individuals with prolonged cognitive difficulties, behavior changes, dizziness, and headache after concussion. MLR is utilized alternating polarity clicks presented monaurally at 70 dB SL at 4 per second, with 40 dB contralateral masking. Five hundred responses were recorded and replicated from Cz-A1 and Cz-A2, with 50 ms. analysis time and 20-1000 Hz filter band pass. SVRs were recorded with the same montage, but used rarefaction clicks, 0.5 Hz stimulus rate, 500 ms. analysis time, and 1-50 Hz filter band pass. Na and Pa MLR components were reduced in amplitude in postconcussion patients. Pa latency was significantly longer in patients than in controls. SVR amplitudes were longer in concussed individuals, but differences in latency and amplitude were not significant. These changes may reflect posttraumatic disturbance in presumed subcortical MLR generators, or in frontal or temporal cortical structures that modulate them. Middle and long-latency auditory evoked potentials may be helpful in the evaluation of postconcussive neuropsychiatric symptoms.

Adult↗

PubMed1995

Effect of frontal and temporal seizure foci on P50 auditory evoked potentials.

Event-related potentials have been occasionally investigated in epilepsy. We recorded P50 auditory evoked potentials in 25 patients with complex partial seizures of frontal and temporal lobe origin. P50 was significantly reduced in amplitude and prolonged in latency in temporal lobe seizure patients as compared to controls. Patients with complex partial seizures originating in the frontal lobes did not differ from controls in P50 amplitude. P50 attenuation differences may be related to interictal behavioral or cognitive changes, but could also reflect medication effects. Event-related potentials may be helpful in differentiating frontal and temporal seizure foci.

Adolescent↗

PubMed1994

Multiple sleep latency tests in epilepsy.

Seizure patients often complain of sleepiness or disturbed sleep. Although susceptible of medication effect, the multiple sleep latency test (MSLT) may quantify daytime sleepiness and help to establish whether qualitative sleep disturbance accompanies epilepsy. In order to measure daytime sleepiness in epilepsy patients, 30 patients with newly diagnosed or presently untreated complex partial seizures had MSLT after an overnight sleep EEG that showed no sleep deprivation or nocturnal seizures. Four 20-minute naps were undertaken at 09:00, 11:00, 13:00, and 15:00, and sleep latency was recorded along with 8 channels of EEG. Twenty of 30 seizure patients reported subjective sleepiness. Eight patients had average sleep latencies less than 8 minutes, and 3 had latencies less than 5 minutes. No sleep onset REM or respiratory disturbance was noted. Twenty-five patients had EEG abnormalities but none had ictal seizures. Right temporal epileptiform activity correlated with sleepiness. MSLT may quantify sleepiness in epilepsy patients, which is common but may be subjective or psychophysiological. Some patients with partial seizures have persistent daytime sleepiness independent of medication, possibly related to residual medication effects or non-specific effect of their epileptogenic foci.

Adult↗

PubMed1993

Contingent negative variation in Gilles de la Tourette syndrome.

The Contingent Negative Variation (CNV) may measure arousal and attention, and is affected by various dopaminergic disorders. We recorded CNVs in 12 patients fulfilling diagnostic criteria of Gilles de la Tourette Syndrome (TS). Ten of 12 patients were male, 10 had attention deficit disorder (ADD), and 3 also had obsessions and compulsions (OCD). Medication had been stopped or TS treatment not yet started. TS patients had higher CNV amplitude and more frequent postimperative negative variation than controls. CNV2 was enhanced in all TS patients, while CNV1 was attenuated in TS patients with ADD or OCD. This suggests that CNV may be increased in TS, mostly because of CNV2 and perhaps due to dopaminergic excess. CNV2, considered to reflect adrenergic arousal mechanisms, may be effected by neurobehavioral concomitants of TS. Neurophysiological categorization of TS patients may be possible and valuable.

Adolescent↗