Generalization as a behavioral window to the neural mechanisms of learning internal models

In generating motor commands, the brain seems to rely on internal models that predict physical dynamics of the limb and the external world. How does the brain compute an internal model? Which neural structures are involved? We consider a task where a force field is applied to the hand, altering the physical dynamics of reaching. Behavioral measures suggest that as the brain adapts to the field, it maps desired sensory states of the arm into estimates of force. If this neural computation is performed via a population code, i.e., via a set of bases, then activity fields of the bases dictate a generalization function that uses errors experienced in a given state to influence performance in any other state. The patterns of generalization suggest that the bases have activity fields that are directionally tuned, but directional tuning may be bimodal. Limb positions as well as contextual cues multiplicatively modulate the gain of tuning. These properties are consistent with the activity fields of cells in the motor cortex and the cerebellum. We suggest that activity fields of cells in these motor regions dictate the way we represent internal models of limb dynamics.     

The effect of retrieval enactment on recall of subject-performed tasks and verbal tasks

The effect of retrieval enactment on memory for nouns (objects) or verbal phrases describing simple actions (e.g., “lift the box”) was addressed in two experiments. In Experiment 1, the type of object involved in the actions was manipulated, with three different types of object being used (body parts, laboratory-related objects, and external objects). In Experiment 2, the integration between the verb-noun pairs was manipulated (well-integrated vs. poorly integrated). Results from both experiments showed that whereas encoding enactment (motor encoding and verbal test) substantially improved the memory performance compared with a verbal condition (verbal encoding and verbal test), retrieval enactment (verbal encoding and motor test) had no major impact on the number of recalled nouns or phrases. Moreover, there was no additional effect of dual enactment (motor encoding and motor test). The overall pattern of the results suggests that there is a fundamental difference between motor processing at encoding and motor processing at retrieval, and the lack of encoding specificity advantage for the motor modality contradicts the view that encoding enactment of verbal commands results in storage of motor representations.     

Electrocortical signs of arousal in response to darkness and the assessment of type A behavior in professional drivers with and without cardiovascular disease

Background and Aims  In night driving, the fatal accident rate is about four times that in daytime. There is a lack of published studies of the effect of darkness on electrocortical responses in professional drivers (PD). Aim: Assessing relations between electroencephalographic (EEG) reactions to enforced darkness reminiscent of night driving, and untoward behavioral response patterns, notably Type A behavior. Methods  PD: 13 with ischemic heart disease, 12 hypertensives (HTN), 10 borderline hypertensives and 34 normotensives, and 23 non-PD controls. Five minutes of electroencephalographic recording with eyes closed, and subsequently 3 minutes exposure to darkness. EEG parameters were: alpha abundance, amplitude and frequent. Type A behavior (TAB) was assessed by observation and by questionnaire. Results  Alpha abundance diminished significantly for darkness compared to spontaneous recording for all groups. No between-group differences were found for EEG. There were no significant differences in EEG between drivers with IHD or HTN taking versus not taking centrally active β-blockers. Drivers with IHD were the only group to show significant increase in dominant α frequency at darkness. The IHD group also had the highest TAB questionnaire scores and the heaviest exposure to professional driving. Type A scores were significantly correlated with dominantt alpha frequency during darkness. Low availability of attachment and special driving hazards best predicted TAB scores in driven. There was a significance between group difference with respect to Symbolic Aversiveness at the work place comparing each driver group with the non-PD control group. Conclusions  Exposure to darkness reminiscent of night driving can elicit central arousal, in conflict with circadian rhythm, and in combination with other driving hazards which contribute to symbolic aversiveness, the essence of driving. And low availability of social attachment could contribute to sustained, and in turn to the development of Type A behavior in professional drivers.     

The role of integration in recognition failure and action memory

In three experiments, we studied memory for action events with respect to exceptions from the Tulving-Wiseman function demonstrated in experiments on recognition failure of recallable words. In Experiment 1, we examined exceptions of poor integration in a regular recognition failure condition (i.e., recognition of targets without contextual cues, followed by recall of targets in the presence of contextual cues). In Experiment 2, we examined exceptions of cue overlap in which subjects also had access to the information of contextual cues at recognition test. In Experiment 3, we attempted to equate the levels of recognition across the action and verbal encoding. In addition, the cue overlap and no-cue overlap conditions were studied in a within-subjects design. Results from the three experiments indicated that encoding enactment (episodic integration) and conceptual integration (semantic integration) are related to each other. As a consequence of this relationship, there is a larger independence between recognition and recall of well-integrated items with encoding enactment. On the other hand, for the poorly integrated items without encoding enactment, there is a larger dependence between recognition and recall. Even in the cue overlap condition, where there is a case of large dependence between recognition and recall, the same pattern of data was observed. The results are discussed in terms of an episodic integration view of encoding enactment.     

Deformation twinning-mediated pseudoelasticity in metal–graphene nanolayered membrane

In this study, we investigated the deformation behaviour of metal–graphene nanolayered composites for five face-centred cubic metals under compression using molecular dynamics simulations. It was found that by increasing the thickness of the individual metal layers, the composite strength increased, while the deformation mechanism changed from buckling to deformation twining in Cu, Au and Ag, which was absent in the monolithic form of those metals of the same orientation and size. The deformation twinning was found to be enabled by the graphene layer, which introduced pseudoelasticity and shape memory effects in the nanolayered membrane with more than 15% recoverable compressive strain.     

Brief Report: Comparing the Autobiographical Remembering of Iranian Immigrant Trauma Survivors with That of Iranian and British Trauma Survivors

This study investigated how culture and posttraumatic stress disorder (PTSD) influence the autobiographical remembering of Iranian trauma survivors living in Britain compared to the remembering of British trauma survivors living in their host culture (Britain) and Iranians in their culture of origin (Iran). Iranian immigrants with and without PTSD completed measures of autobiographical remembering. Data was compared to previously collected data from British and Iranian trauma survivors with and without PTSD. It was found that the memory‐content of Iranian immigrants' memories resembled that of Iranian trauma survivors in Iran, while the phenomenological properties of their autobiographical remembering more closely resembled that of British trauma survivors. Moreover, there were pan‐cultural distortions and deficits in the autobiographical remembering of those with PTSD. The findings suggest that immigrants with PTSD have similar disruptions and distortions in their autobiographical remembering as that of individuals with PTSD living in their host culture and culture of origin.Copyright © 2016 John Wiley & Sons, Ltd.     

Exploring Emotive Verbs in Persian and English Short Stories: A Contrastive Sociopragmatic Approach

Current developments in the areas of discourse analysis and cross-cultural studies have led to an increased interest in the way people of different cultures express their affections on various occasions. Individuals learn how to regulate their emotional reactions according to sociocultural norms of behavior defined by the cultures to which they belong. Accordingly, this article aimed to investigate the linguistic expression of emotions in English and Persian short stories in order to fathom out the impact of culture on the way feelings are expressed cross-culturally. For this purpose, a corpus of eight different English and Persian short stories, four in each language, was selected based on a purposive sampling method. Then, using Devon’s (The origin of emotions, 2006) typology of emotions, different types of emotive verbs were selected as the unit of analysis. Finally, the frequency and percentage values of emotive verb tokens used in these stories were carefully tabulated in terms of types and their respective metalinguistic categories introduced by Wierzbicka (Emotions across languages and cultures: diversity and universals, Cambridge University Press, Cambridge, 1999). The results obtained from the analysis of the targeted corpora reflected that English and Persian writers employ different types of emotive verbs in expressing their feelings. Essentially, the findings of the present study may have important implications for language teachers, material developers, and course designers.