Anke Bouma

The development of lateral event-related potentials (ERPs) related to word naming: A four year longitudinal study.

Event-related potentials (ERPs) were recorded from the left and right temporal and parietal sites during a word naming task. Subjects were a group of children that were followed over four consecutive years starting at Kindergarten. ERP waveforms contained a sequence of positive and negative components (N150, P240, N360, N530 and SW). All components, except N150, showed changes in amplitude as a function of age, whereas SW, N360 and N150 also changed in hemispheric distribution. In addition, a relationship was found between reading performance and ERP amplitudes over the right parietal hemisphere in young children, and over the left temporal hemisphere in older children. Proficient readers showed larger (more negative) parietal N530 amplitudes than less proficient readers, especially when stimuli were degraded words. The results are discussed in terms of age-related changes in right and left hemisphere functions involved in early and advanced stages of reading, that might possibly be related to visual word recognition.

Cortical responses to word reading by right- and left-eared normal and reading disturbed children.

Abstract There is behavioral evidence that children showing left ear dominance (LED) generate hemispheric reading strategies which are different from those who show right ear dominance (RED) subsequent to dichotic verbal stimulation. Electrophysiological evidence of this was sought in the present investigation. Normal and reading-disturbed children were required to read monosyllabic words that were flashed at the point of fixation. Event-related potentials (ERP) were analysed in relation to reading level (normal vs disturbed readers), ear dominance (LED vs RED), and side of diversion (left temporal vs right temporal and left parietal vs right parietal). Significant interactions were found for P310 and N440 amplitudes and latencies, indicating that normal and reading-disturbed LED and RED children generate different reading strategies.

Influence of transcutaneous electrical nerve stimulation on memory in patients with dementia of the Alzheimer type

This study examined the effect of transcutaneous electrical nerve stimulation (TENS) on memory in patients with dementia of the Alzheimer type. It was hypothesized that, in the early stage of the illness, electrical stimulation could activate the affected cortical regions by stimulating the neurotransmitter systems projecting to these areas. The results reveal that electrical stimulation improves the verbal long-term memory in these patients. Moreover, verbal fluency improves more in patients who received electrical stimulation than in patients who received control treatment. However, electrical stimulation does not influence the visual long-term memory of the patients, nor does it affect their verbal and nonverbal short-term memory. Underlying theoretical mechanisms are discussed.

Cerebral organization of verbal and motor functions in left-handed and right-handed adults: effects of concurrent verbal tasks on unimanual tapping performance.

Two experiments were conducted to study the interference effects of different concurrent verbal tasks on unimanual single-finger tapping and unimanual sequential finger tapping. Experiment 1 involved 24 right-handed university students. In the dual-task conditions, right-handers showed a greater right-hand than left-hand performance reduction for single-finger tapping, and an equal right-hand and left-hand reduction for sequential tapping. Experiment 2 involved 60 left-handed university students, divided into four groups according to familial sinistrality and writing hand posture. In the dual-task conditions, left-handers showed a greater left-hand than right-hand performance reduction for single-finger tapping, and an equal left-hand and right-hand reduction for sequential finger tapping. A dichotic listening task revealed a left hemispheric dominance for auditory linguistic functioning in most of the left-handers. Familial sinistrality and hand posture, on the whole, did not influence tapping performances. However, these factors influenced the ear asymmetries on the dichotic listening task. It is speculated that, with single-finger tapping, interference only takes place beyond the point of language motor programming, that is to say, at the motor areas and the supplementary motor areas of the cortex.

Grade-related changes in event-related potentials (ERPs) in primary school children: Differences between two reading tasks.

Event-related potentials (ERPs) were recorded from the left and right temporal and parietal sites during word reading in a group of children who were followed over three consecutive years, starting at Grade 1. The first task required the child to read repeatedly presented words; the second task consisted of a series of different words, with each word being presented only once. All ERP components showed changes in amplitude as a function of grade: P240, N530, the parietal N150, and SW all decreased, whereas the temporal N360 and SW both increased. In addition, SW changed from no asymmetry to larger positivity over the right site, whereas N360 changed from symmetric amplitudes to larger amplitudes over the left hemisphere with grade. Single word presentations were associated with smaller SW activity and larger N530 and N360 amplitudes than were repeated word presentations. It was also found that proficient readers showed larger SW and N360 asymmetries and shorter vocal response times than did less proficient readers. In addition, a positive relationship was found between reading performance and ERP amplitudes over the left temporal hemisphere at Grades 2 and 3, particularly in the single word reading task. The results are discussed in terms of age-related changes in right and left hemisphere functions involved in learning to read.

Mental rotation of laterally presented random shapes in males and females.

Eighteen right-handed subjects (9 males, 9 female) were to decide if laterally presented random shapes were identical or a mirror image of a centrally presented standard shape. The lateral shapes were rotated over 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees, or 300 degrees. For unrotated (0 degrees) mirror image stimuli, females showed a significant right visual-field advantage, whereas males showed no significant hemifield effect. The rate of rotation was equivalent for both sexes. Field of presentation did not affect the rotation rate either. The present results support a growing number of findings that indicate that the interpretation of mental rotation as a typical right-hemispheric spatial-processing task is questionable.

Familial resemblance for cognitive abilities in families with P-type dyslexic, L-type dyslexic, or normal reading boys

P-type dyslexic, L-type dyslexic, and normal reading boys, and their parents were administered a number of cognitive tasks. The P- and L-type dyslexic boys showed impaired performances on tasks representing a verbal/memory dimension. In addition, L-type dyslexics performed worse on a figure-rotation task, a result that supported the notion of a visuospatial deficit in this type of reading disturbance. The parents of P- and L-type dyslexics exhibited lowered performances on verbal/memory tasks, but they showed no evidence of impaired visuospatial functioning. Indices of familial resemblance revealed differential familial resemblances in the three types of families. In the families of P-type dyslexics, a high father-son effect was found for the visuospatial dimension. In the families of L-type dyslexics, moderately high single-parent/child effects were found for both fathers and mothers and for both the verbal/memory dimension and the visuospatial dimension. In the families of normal readers, only small single-parent/child effects were found.

Effects of visual-field and matching instruction on event-related potentials and reaction time.

Vertical letter pairs were presented randomly in the left and right visual hemifields in a physical identity match and name identity match condition. The reaction times showed a right visual field superiority for name matches, and a left visual field superiority for physical matches. Event-related potentials to letter pairs showed a sequence of three waves: a negative wave (N2, around 270 msec), a positive wave (P3, around 500 msec), and a broad positive slow wave (SW, around 600-700 msec), respectively. P3 and SW amplitudes were consistently larger at the left hemisphere than at the right hemisphere, regardless of the field of stimulation. At both hemispheres, N2 waves were always larger to stimuli presented in the visual field contralateral to a hemisphere than stimuli presented in the visual field ipsilateral to a hemisphere. The positive waves (P3, SW) showed the opposite pattern: smaller amplitudes to stimuli that were presented contralaterally than stimuli that were presented ipsilaterally to a given hemisphere. These results were attributed to a shift in sustained negativity on the directly stimulated hemisphere, relative to the indirectly stimulated hemisphere, reflecting either sensory at attentional processes in the posterior cerebral hemispheres.

Qualitative analysis of the drawings of alzheimer patients

Abstract The qualitative aspects of drawing errors made on a drawing-from-memory task in 10 AD patients are compared to those made by 10 normal control subjects. In a subgroup of AD patients, we studied the deterioration in drawing performance by retesting them a year later. The pattern of drawing performance was also examined on two other tasks in which the memory component plays a minimal role (copying and tracing of objects). The results of all drawing tasks revealed qualitative differences in drawing disability between AD patients and control subjects. In the longitudinal study, it was found that some types of drawing errors were more susceptible to deterioration than were other error types. The possible mechanisms playing a role in the different types of drawing errors are discussed. It is suggested that some error types may be considered as compensatory strategies for defective components of the drawing task.

Selective activation effects of concurrent verbal and spatial memory loads in left-handed and right-handed adults

Thirty-two left-handed subjects, divided into four groups according to sex and familial sinistrality, and 16 right-handed subjects without familial sinistrality (8 male, 8 female) participated in a tachistoscopic unilateral letter-identification task with concurrent verbal- and spatial-memory loads. Across groups, a significant right visual field advantage for letter-identification was found. In the majority of both left-handed and right-handed subjects, the concurrent verbal-memory load resulted in a selective activation, with the right visual field performance showing improvement. However, the group of left-handed males with a positive family history of sinistrality gave less evidence of selective left-hemispheric activation as a consequence of the verbal-memory load. The concurrent spatial-memory load did not result in a consistent pattern of selective activation.