Biomedical subjects

J Matt

Publications and source records attributed to J Matt.

6 recordsLinked to original sources

PubMed1995

Metamemory, distinctiveness, and event-related potentials in recognition memory for faces.

A neglected topic in metamemory research is the ability of subjects to predict their own recognition performance for faces. We investigated whether subjects can make such judgments of learning (JOL) for unfamiliar faces and whether JOLs relate to facial distinctiveness, a powerful determinant of face recognition. One group of subjects made JOLs, and a second group rated the same faces for distinctiveness; subsequently, both groups tried to recognize these faces among new faces. There was significant prospective metamemory for faces that appeared to be based on facial distinctiveness. Both prospective metamemory and distinctiveness ratings related to long-lasting effects in event-related brain potentials (ERPs), closely resembling an ERP component that predicted face recognition. Therefore, the brain processes underlying JOLs, distinctiveness, and recognition memory for faces appear to be intimately related.

Adult↗

PubMed1992

Differential effects of voluntary expectancies on reaction times and event-related potentials: evidence for automatic and controlled expectancies.

Expectancy has been used to explain the effects of stimulus sequences both on reaction times (RTs) and on the P300 component of the human event-related potential. However, there are conflicting views about the control obtainable over these underlying expectancies. We compared the effects of voluntary expectancies for stimulus changes or repetitions in random tone series on RTs and the P300. Ss responded according to either stimulus identity (Experiment 1) or stimulus sequence (Experiment 2). In both experiments RTs were strongly affected by event expectedness. P300 amplitude, on the other hand, was affected (as a trend) only in Experiment 2. The results suggest that there are at least 2 types of "expectancy", one that is largely automatic and inflexible, reflected in P300 amplitude, and a second, controlled process that is reflected mainly in RT. The latter type of expectancy appears to affect processing stages beyond stimulus evaluation and classification.

Arousal↗

PubMed1991

Human brain potential correlates of face encoding into memory.

ERPs elicited by photographs of unfamiliar faces were shown to be predictive for their later recognition. We established that these ERP differences were unrelated to fluctuations of attention or other non-specific factors during perceptual processing. Therefore they may be interpreted as manifestations of brain processes that correlate with memory encoding. The scalp topography of this ERP difference was bipolar with greater electrical positivity at frontal and greater negativity at parieto-temporal scalp sites. This topography appears to contrast with the more uniformly positive differences reported for verbal stimuli but is in accord with what might be expected for faces and complex visual stimuli.

Adult↗

PubMed1990

Consciousness of attention and expectancy as reflected in event-related potentials and reaction times.

The effects of conscious expectancies and attention on event-related potentials (ERP) and choice reaction times (RT) and their modulation by stimulus sequence were studied. Subjects retrospectively reported their expectancy of, and attention to, the terminal tones of short series. ERPs and RTs showed the usual sequential effects that were modulated by practice. As ratings were affected by only a few of the stimulus sequence, conscious access to sequence-based expectancy or attention appears to be fragmentary. Increased P300 amplitude with attention indicates conscious access to processing capacity. RTs and P300 latencies suggest stimulus processing time to decrease with sequence-based and consciously accessible expectancy. Differential effects of stimulus sequences and conscious expectancies on P300 amplitude indicate influences of two varieties of expectancy.

Arousal↗

PubMed1990

Awareness of P300-related cognitive processes: a signal detection approach.

Although the P300 component of the human event-related potential is purported to indicate consciousness of an event, it is unclear which of the P300-related processes, if any, are accessible to awareness. This study explored awareness of such processes in Bernoulli series of auditory stimuli using signal detection theory and selective averaging of ERPs according to the subjects' classifications. Following targets eliciting appropriate P300 amplitudes, the subject was requested to classify his brain response as small, medium, or large, whereupon visual feedback was given about the correctness of the response. Averaging the ERPs according to the subjects' classifications showed P300 amplitudes to increase with the classification category, whereas the prestimulus and post-P300 event-related potentials were unrelated to the category. Signal detection analysis revealed non-zero sensitivity measures for the P300 amplitude categories. Although no conclusive suggestion can be made at present as to the basis of the P300 discrimination ability found here, it was possible to rule out electro-ocular and electromyographic activity, the preceding auditory stimulus, and the prior feedback given, as cues for discrimination.

Adult↗

PubMedDate not supplied

Treatment of irradiation-induced mucositis with growth factors (rhGM-CSF) in patients with head and neck cancer.

BACKGROUND: Mucositis is a frequent side-effect of radiotherapy which often causes interruption of therapy and consequently decreases the probability of remission or cure, rhGM-CSF may ameliorate symptoms of mucositis by increasing the immune response via macrophage activation and stimulation of secondary cytokines. PATIENTS AND METHODS: 32 patients with locally advanced head and neck cancer were treated with adjuvant local radiotherapy after surgery (60 Gy in 30 dose fractions). In a pilot study, 16 patients received rhGM-CSF for five days, starting after a radiation dose of 20 Gy. These patients were compared retrospectively with a control group of 16 matching patients. Patients were assessed according to the Oral Assessment Guide (OAG), the Composite Mucositis Score (CMS) and the Common Toxicity Criteria (CTC) for severity of mucositis and pain. RESULTS: When compared with controls, patients on rhGM-CSF treatment showed decreased OAG, CMS and CTC scores. During the following irradiation courses mucositis was less severe in patients previously treated with rhGM-CSF. With regard to pain relief, rhGM-CSF-treated patients demonstrated a statistically significant improvement (p = 0.011), compared with controls. CONCLUSION: rhGM-CSF affected the severity of oral mucositis and reduced the related pain. As rhGM-CSF was well tolerated, this effect will be further investigated in prospective, controlled study.

Granulocyte-Macrophage Colony-Stimulating Factor↗