Comprensión del lenguaje y potenciales evocados

Resumen

En este trabajo se pretende dar cuenta de los últimos adelantos en el campo de los procesos relacionados con la comprensión del lenguaje y los potenciales evocados. Estos han mostrado ser herramientas útiles para el estudio de dichos procesos. Para ello se revisan una serie de estudios relacionados con los componentes que clásicamente han venido recibiendo una mayor atención. Así, el Potencial de Reconocimiento y la N400, parecen guardar relación con aspectos semánticos. Por otro lado, la Negatividad Izquierda Anterior Temprana y la P600 estarían más relacionados con los sintácticos. También se mencionan otros componentes, como la P300 y algunos que ha recibido menor atención.     

Tool-use and the left hemisphere: What is lost in ideomotor apraxia?

Impaired tool related action in ideomotor apraxia is normally ascribed to loss of sensorimotor memories for habitual actions (engrams), but this account has not been tested against a hypothesis of a general deficit in representation of hand-object spatial relationships. Rapid reaching for familiar tools was compared with reaching for abstract objects in apraxic patients (N = 9) and in a control group with right hemisphere posterior stroke. The apraxic patients alone showed an impairment in rotating the wrist to correctly grasp an inverted tool but not when inverting the hand to avoid a barrier and grasp an abstract object, and the severity of the impairment in tool reaching correlated with pantomime of tool-use. A second experiment with two apraxic patients tested whether barrier avoidance was simply less spatially demanding than reaching for a tool. However, the patient with damage limited to the inferior parietal lobe still showed a selective problem for tools. These results demonstrate that some apraxic patients are selectively impaired in their interaction with familiar tools, and this cannot be explained by the demands of the task on postural or spatial representation. However, traditional engram theory cannot account for associated problems with imitation of novel actions nor the absence of any correlated deficit in recognition of the methods of grasp of common tools. A revised theory is presented which follows the dorsal and ventral streams model ( Milner & Goodale, 2008) and proposes preservation of motor control by the dorsal stream but impaired modulating input to it from the conceptual systems of the left temporal lobe.     

Impulsivity,self-control,and hypnotic suggestibility

Hypnotic responding might be due to attenuated frontal lobe functioning after the hypnotic induction. Little is known about whether personality traits linked with frontal functioning are associated with responsiveness to hypnotic suggestions. We assessed whether hypnotic suggestibility is related to the traits of self-control and impulsivity in 154 participants who completed the Brief Self-Control Scale, the Self-Regulation Scale, the Barratt Impulsiveness Scale (BIS-11), and the Harvard Group Scale of Hypnotic Susceptibility (HGSHS:A). BIS-11 non-planning impulsivity correlated positively with HGSHS:A (Bonferroni-corrected). Furthermore, in the best model emerging from a stepwise multiple regression, both non-planning impulsivity and self-control positively predicted hypnotic suggestibility, and there was an interaction of BIS-11 motor impulsivity with gender. For men only, motor impulsivity tended to predict hypnotic suggestibility. Hypnotic suggestibility is associated with personality traits linked with frontal functioning, and hypnotic responding in men and women might differ.     

Narrative retelling in children with neurodevelopmental disorders: Is there a role for nonverbal temporal‐sequencing skills?

Oral narrative retelling is often problematic for children with communicative and neurodevelopmental disorders. However, beyond a suggested role of language level, little is known about the basis of narrative performance. In this study we examine whether oral narrative retelling might be associated not just with language level but also with skills related to nonverbal narrative temporal sequencing. A diagnostically heterogeneous sample of Swedish‐speaking children with a full scale IQ >70 was included in the study (N = 55; age 6–9 years). Narrative retelling skills were measured using the three subscores from the bus story test (BST). Independent predictors included (1) temporal sequencing skills according to a picture arrangement test and (2) a language skills factor consisting of definitional vocabulary and receptive grammar. Regression analyses show that language skills predicted BST Sentence Length and Subordinate Clauses subscores, while both temporal sequencing and language were independently linked with the BST Information subscore. When subdividing the sample based on nonverbal temporal sequencing level, a significant subgroup difference was found only for BST Information. Finally, a principal component analysis shows that temporal sequencing and BST Information loaded on a common factor, separately from the language measures. It is concluded that language level is an important correlate of narrative performance more generally in this diagnostically heterogeneous sample, and that nonverbal temporal sequencing functions are important especially for conveying story information. Theoretical and clinical implications are discussed.     

A New Tactile Illusion: Temporal Limits on the Processing of Spatiotemporal Patterns

A novel illusion was observed when 12 tactile point-stimulators arranged in a circle were sequentially activated so that each quadrant was first traced in a clockwise manner, then counterclockwise, and again in a clockwise manner, after which the next quadrant was similarly traced. Under certain temporal conditions this stimulus pattern was experienced as a point moving through an overall circular path but looping inwardly about once per quadrant. The effects of variations in rate of presentation of such stimuli were investigated by having subjects make drawings of their perceptual experiences. Three skin surfaces were used (palm, fingers, and forearm), and all produced similar results except for lower confidence and reliability of drawings made from forearm stimulation. Pattern presentation rate, however, had a consistent and powerful effect, with the looping illusion most frequently observed at rates around 25 pattern points per s and with different perceptual organizations dominating as rates departed widely from this optimum. The illusory perceptual organizations were interpreted as compromises between past and present stimulation necessitated by the relative slowness of tactile processing of spatio-temporal patterns.     

Understanding anterograde amnesia: Disconnections and hidden lesions

Three emerging strands of evidence are helping to resolve the causes of the anterograde amnesia associated with damage to the diencephalon. First, new anatomical studies have refined our understanding of the links between diencephalic and temporal brain regions associated with amnesia. These studies direct attention to the limited numbers of routes linking the two regions. Second, neuropsychological studies of patients with colloid cysts confirm the importance of at least one of these routes, the fornix, for episodic memory. By combining these anatomical and neuropsychological data strong evidence emerges for the view that damage to hippocampal—mammillary body—anterior thalamic interactions is sufficient to induce amnesia. A third development is the possibility that the retrosplenial cortex provides an integrating link in this functional system. Furthermore, recent evidence indicates that the retrosplenial cortex may suffer “covert” pathology (i.e., it is functionally lesioned) following damage to the anterior thalamic nuclei or hippocampus. This shared indirect “lesion” effect on the retrosplenial cortex not only broadens our concept of the neural basis of amnesia but may also help to explain the many similarities between temporal lobe and diencephalic amnesia.     

Probing the Brain Substrates of Cognitive Processes Responsible for Context Effects on Recognition Memory

ABSTRACT

Context effects on episodic recognition memory involve separable contributions of target-context binding, additive familiarity, and configural constancy. Here we examine whether these factors reflect contributions of processes attributed to different brain substrates. First, we challenged frontal and medial temporal lobe-based cognitive capacities in healthy young adults, employing divided attention tasks at encoding and retrieval, and extended retrieval delay, respectively. Target-context binding effects were specifically attenuated by delay, but not by divided attention. In a second experiment, older adults were identified by neuropsychological testing as having different levels of frontal and medial temporal lobe-dependent cognitive functions. Consistent with Experiment 1, older adults with low medial temporal lobe function exhibited reduced target-context binding effects, but levels of frontal function did not modulate binding effects. These findings indicate that unlike source memory, context effects on memory are associated with the integrity of medial temporal lobe-based processes but not with the integrity of frontal lobe-based processes. Our findings also emphasize the importance of discriminating between functional subgroups in the attempt to characterize memory processes in older adults.