Posttraumatic stress disorder is associated with limited executive resources in a working memory task

Patients with posttraumatic stress disorder (PTSD) can show declines in working memory. A dual-task design was used to determine whether these impairments are linked to executive control limitations. Participants performed a Sternberg memory task with either one or four letters. In the dual-task condition, the maintenance period was filled with an arrow flanker task. PTSD patients were less accurate on the working memory task than were controls, especially in the dual-task condition. In the single-task condition, both groups showed similar patterns of brain potentials from 300 to 500 ms when discriminating old and new probes. However, when taxed with an additional task, the event-related potentials (ERPs) of the PTSD group no longer differentiated old and new probes. In contrast, interference resolution processes in both the single- and dual-task conditions of the flanker task were intact. The lack of differentiation in the ERPs reflects impaired working memory performance under more difficult, dual-task conditions. Exacerbated difficulty in performing a working memory task with concurrent task demands suggests a specific limitation in executive control resources in PTSD.     

Interpreting dissociations between regular and irregular past-tense morphology: Evidence from event-related potentials

Neuropsychological dissociations between regular and irregular English past-tense morphology have been reported using a lexical decision task in which past-tense primes immediately precede present-tense targets. We present N400 event-related potential data from healthy participants using the same design. Both regular and irregular past-tense forms primed corresponding present-tense forms, but with a longer duration for irregular verbs. Phonological control conditions suggested that differences in formal overlap between prime and target contribute to, but do not account for, this difference, suggesting a link between irregular morphology and semantics. Further analysis dividing the irregular verbs into two categories (weak irregular and strong) revealed that priming for strong verbs was reliably stronger than that for weak irregular and regular verbs, which were statistically indistinguishable from one another. We argue that, although we observe a regular-irregular dissociation, the nature of this dissociation is more consistent with single- than with dual-system models of inflectional morphology.     

Mood states during a successful world record underwater diving attempt

The mood states of a diver were recorded over a period of almost 10 days of submersion. Scores on the Profile of Mood States obtained on the components of Depression, Anger, and Confusion suggested that there were no signs of psychological disintegration over this period. As expected, scores on Fatigue increased whereas perceived Vigor diminished over time. High Esteem remained consistent. It is proposed that profiling of mood states can be a useful monitoring tool of an acclimatization process.     

Constraint, alcoholism, and electrodermal response in aversive classical conditioning and mismatch novelty paradigms

This study investigated whether low levels of the personality trait of constraint and early-onset alcoholism would be associated with deficits in aversive conditioning and smaller responses to novelty in a stimulus mismatch protocol. Personality traits (constraint and socialization) and skin conductance responses (SCRs) during conditioning and novelty paradigms were assessed in alcoholics (n=41) and non-alcoholics (n=32). The conditioning protocol involved measuring SCRs after conditioned stimuli (CS+: tones) paired with shock, CS− tones unpaired with shock, and CS+ probes unpaired with shock. The mismatch protocol involved measuring SCRs to auditory stimuli consisting of a series of 5 pure tones of the same pitch followed a shorter white noise stimulus (the novel stimulus). Contrary to the hypothesis, alcoholics did not differ from non-alcoholics in SCRs to CS+ probes or on the mismatch measure (SCR novel tone—SCR to 5^th tone). Higher levels of constraint and self-reports of fear during conditioning were associated with smaller responses to both the CS+ probes and the CS− tones as well as the mismatch measure within non-alcoholics, but not within alcoholics. In alcoholics, low constraint was associated with greater habituation to CS+ probes, and poor differential conditioning on measures of change across trials in SCR to CS+ probes and CS− stimuli. The results suggest that different processes influence levels of constraint in non-alcoholics and alcoholics. The data indicate that low constraint in non-alcoholics is associated with allocating fewer processing resources to potentially significant stimuli, rather than being associated with a specific deficit in aversive conditioning per se.     

Cerebellar patients demonstrate preserved implicit knowledge of association strengths in musical sequences

Recent findings suggest the involvement of the cerebellum in perceptual and cognitive tasks. Our study investigated whether cerebellar patients show musical priming based on implicit knowledge of tonal-harmonic music. Participants performed speeded phoneme identification on sung target chords, which were either related or less-related to prime contexts in terms of the tonal-harmonic system. As groups, both cerebellar patients and age-matched controls showed facilitated processing for related targets, as previously observed for healthy young adults. The outcome suggests that an intact cerebellum is not mandatory for accessing implicit knowledge stored in long-term memory and for its influence on perception. One patient showed facilitated processing for less-related targets (suggesting sensory priming). The findings suggest directions for future research on auditory perception in cerebellar patients to further our understanding of cerebellar functions.