Biomedical subjects

Grant J Carroll

Publications and source records attributed to Grant J Carroll.

3 recordsLinked to original sources

PubMed2006

Frequent lapses of responsiveness during an extended visuomotor tracking task in non-sleep-deprived subjects.

We investigated the occurrence of lapses of responsiveness (lapses) in 15 non-sleep-deprived subjects performing a 1D continuous tracking task during normal working hours. Tracking behaviour, facial video, and electroencephalogram (EEG) were recorded simultaneously during two 1-h sessions. Rate and duration were estimated for lapses identified by a tracking flat spot and/or video sleep. Fourteen of the 15 subjects had one or more lapses, with an overall rate of 39.3 +/- 12.9 lapses per hour (mean +/- SE) and a lapse duration of 3.4 +/- 0.5 s. We also found that subjects' performance improved towards the end of the 1-h long session, even though no external temporal cues were available. Spectral power was found to be higher during lapses in the delta, theta, and alpha bands, and lower in the beta, gamma, and higher bands, but correlations between changes in EEG power and lapses were low. In conclusion, lapses are a frequent phenomenon in normal subjects - even when not sleep-deprived - engaged in an extended monotonous continuous visuomotor task. This is of particular importance to the transport sector in which there is a need to maintain sustained attention for extended periods of time and in which lapses can lead to multiple-fatality accidents.

Adolescent↗

PubMed2005

Slow-wave activity arising from the same area as epileptiform activity in the EEG of paediatric patients with focal epilepsy.

OBJECTIVE: The aim of this study was to investigate the presence and characteristics of apparent non-epileptiform activity arising in the same brain area as epileptiform activity in the EEG of paediatric patients with focal epilepsy. METHODS: The EEG from eight patients was analysed by an automated method which detects epochs with a single underlying source having a dipolar potential distribution. The EEG with the highlighted detections was then rated by a clinical neurophysiologist (EEGer) with respect to epileptiform activity. RESULTS: Although EEGer-marked events and computer detections often coincided, in five out of the eight patients, a substantial number of other detections were found to arise from the same area as the marked events. The morphology of a high proportion of these other detections did not resemble typical epileptiform activity and had a frequency content mainly in the delta and theta ranges. CONCLUSIONS: This is, to our knowledge, the first study to use an automated technique to demonstrate the presence of non-epileptiform activity arising from the same area as the epileptiform activity in the EEG of paediatric patients with focal epilepsy. This slow wave activity is likely to be related to the underlying epileptogenic process. SIGNIFICANCE: This paper suggests a technique for automated detection of focal activity arising from epileptogenic foci. It also provides a new perspective on extracting clinical useful information from slow-wave background EEG activity.

Brain Mapping↗

PubMed2003

Posttraumatic stress disorder: do electrical startle responses and thyroid function usefully supplement self-report? A study of Vietnam War veterans.

OBJECTIVE: To investigate the usefulness of electrical startle responses and thyroid function as supplements to self-report measures of posttraumatic stress disorder (PTSD). METHOD: Invitations were sent to all New Zealand Vietnam War veterans known to be living in North Canterbury; 50 responded and the 35 living in or near Christchurch were included. Self-report measures of PTSD (the Davidson Trauma Scale (DTS) and the Symptom Check List (SCL-90-R) ), an eye blink electrical startle response and thyroid function were measured. The DTS was re-administered one to two weeks later to assess short-term test-retest reliability. Six months later the DTS and the electrical startle response were measured again. RESULTS: The veterans reported a wide range of PTSD severity, with 15/35 reporting prior diagnosis of PTSD. The DTS showed high short-term test-retest reliability (r = 0.93) and a moderate correlation after 6 months (r = 0.73). It also showed sensitivity to change; in one to two weeks the scores increased by nearly half a standard deviation, possibly because of an imminent "homecoming" march. The DTS and a PTSD scale from the SCL-90-R were highly correlated (r = 0.89). The total triiodothyronine (T3) to free thyroxine (T4) ratio measure of thyroid function correlated poorly with self-report (r < or = 0.27). The electrical startle response also correlated poorly with self-report (r < or = 0.26), showed low internal consistency between left and right sides (r = 0.43), and correlated 0.39 over six months. It was disliked by the veterans and had increased slightly at 6 month follow-up, perhaps because of sensitization. CONCLUSIONS: The DTS was reliable and correlated highly with the SCL-90-R PTSD scale. Neither thyroid function nor eye blink electrical startle correlated with each other or with self-report, and reliability was not good for electrical startle. These two measures do not appear to add anything useful to the assessment of PTSD.

Aged↗