Contributions of volumetrics of the hippocampus and thalamus to verbal memory in temporal lobe epilepsy patients

Recent theories have posited that the hippocampus and thalamus serve distinct, yet related, roles in episodic memory. Whereas the hippocampus has been implicated in long-term memory encoding and storage, the thalamus, as a whole, has been implicated in the selection of items for subsequent encoding and the use of retrieval strategies. However, dissociating the memory impairment that occurs following thalamic injury as distinguished from that following hippocampal injury has proven difficult. This study examined relationships between MRI volumetric measures of the hippocampus and thalamus and their contributions to prose and rote verbal memory functioning in 18 patients with intractable temporal lobe epilepsy (TLE). Results revealed that bilateral hippocampal and thalamic volume independently predicted delayed prose verbal memory functioning. However, bilateral hippocampal, but not thalamic, volume predicted delayed rote verbal memory functioning. Follow-up analyses indicated that bilateral thalamic volume independently predicted immediate prose, but not immediate rote, verbal recall, whereas bilateral hippocampal volume was not associated with any of these immediate memory measures. These findings underscore the cognitive significance of thalamic atrophy in chronic TLE, demonstrating that hippocampal and thalamic volume make quantitatively, and perhaps qualitatively, distinct contributions to episodic memory functioning in TLE patients. They are also consistent with theories proposing that the hippocampus supports long-term memory encoding and storage, whereas the thalamus is implicated in the executive aspects of episodic memory.     

Additional-singleton interference in efficient visual search: A common salience route for detection and compound tasks

In efficient search for feature singleton targets, additional singletons (ASs) defined in a nontarget dimension are frequently found to interfere with performance. All search tasks that are processed via a spatial saliency map of the display would be predicted to be subject to such AS interference. In contrast, dual-route models, such as feature integration theory, assume that singletons are detected not via a saliency map, but via a nonspatial route that is immune to interference from cross-dimensional ASs. Consistent with this, a number of studies have reported absent interference effects in detection tasks. However, recent work suggests that the failure to find such effects may be due to the particular frequencies at which ASs were presented, as well as to their relative saliency. These two factors were examined in the present study. In contrast to previous reports, cross-dimensional ASs were found to slow detection (target-present and target-absent) responses, modulated by both their frequency of occurrence and saliency (relative to the target). These findings challenge dual-route models and support single-route models, such as dimension weighting and guided search.     

Prevalence and functions of stereotyped behaviors in nonhandicapped children in residential care

Caregivers in nine residential care institutions rated the occurrence of 15 stereotyped behaviors in 142 nonhandicapped children aged from 10 months to 11 years. The frequency and duration of each stereotypy as well as the typical situations in which it occurred were assessed. The most frequent stereotypies were thumbsucking, hair twisting, and body rocking in infants and young children; thumbsucking and making faces in preschool-age children; and nail biting/chewing in school-age children. Boys exhibited stereotypies more frequently than girls, and children with a suspected history of child abuse more frequently than other children. Typical situations for stereotypies could be classified to four types: concentration/demand, arousal/frustration, boredom/monotony, and stimulation/distraction. Nail biting/chewing and lip biting occurred predominantly in concentration/demand; thumbsucking and hair twisting in boredom/monotony; and pulling faces and scratching oneself in arousal/frustration and concentration/demand situations. These results provide preliminary indications regarding the different functions of individual stereotypies.The author would like to thank Jonathan Harrow (University of Bielefeld) for translating this paper from German into English.     

Voice Onset Time in Ataxic Dysarthria

In eight patients with a purely ataxic syndrome due to cerebellar atrophy the voice onset time (VOT) of word-initial stop consonants was measured at the acoustic signal. The subjects had been asked to produce sentence utterances including either one of the German minimal pair cognates “Daten” (/datn/, “data”) and “Taten” (/tatn/, “deeds”). In addition, a master tape comprising the target words from patients and controls in randomized order was played to six listeners for perceptual evaluation. Two major findings emerged. First, the cerebellar subjects presented with a reduced categorical distinction of the VOT of voiced and unvoiced stop consonants. Second, the patients' target words with initial unvoiced plosive gave rise to a significantly increased number of misassignments at perceptual evaluation. To some extent comparable VOT disruptions have been noted in apraxia of speech and basal ganglia disorders. Thus, different pathomechanisms might result in similar VOT abnormalities.     

An experimental study of social performance and delay on the testimonial validity of story recall

Sixty adults from the city of Linz took part in this experiment. They read a story—The War of the Ghosts—in pairs, and were required to reproduce it either jointly, in dyads, or singly, and either immediately following or one week later. In addition they were asked a number of specific questions about the story, and gave various ratings of confidence and completeness. As predicted, social (dyadic) performance increased confidence, completeness and the incidence of implicational errors (errors which do not contradict the original). Delay significantly diminished confidence. Analyses of confidence for right and wrong answers indicated that subjective testimonial validity was substantial in all conditions. Analyses of objective testimonial validity showed that dyads are more trustworthy than individuals when they are correct, but are less trustworthy when they happen to be wrong. They overall conjidence I accuracy correlation across conditions of +0.6 masks the fact that the greatest obstacle to valid testimony is inappropriate confidence in wrong answers, especially in dyads, and especially immediately after the event. The incidence of implicational errors was highly related positively to measures of confidence and accuracy, whereas confusional errors were independent. Implicational errors are regarded as an especially important element in schematic recall, and are an important aspect of the superiority of social performance.