Gregorio Gómez-Jarabo

The Recognition Potential: An ERP Index of Lexical Access ☆

Recognition potential (RP) is a brain electrical response that appears when a subject views recognizable images of words. However, it has yet to be determined whether the processes reflected by RP are related to orthographic or to semantic analysis. This study aimed to resolve this question by studying the RP evoked by orthographically correct stimuli that were devoid of meaning. Results showed RP not only to this type of stimuli, but also to others achieving lower levels in the reading process. Strikingly, however, the RP amplitude significantly differed in parallel with the levels of the reading processes attained by the stimuli, the amplitude of the RP progressively increasing as the level approached the semantic one, which showed the highest amplitude. These results not only confirm the replicability of RP, but also its promise of potential usefulness in the study and assessment of language perception.

MDMA-Assisted Psychotherapy Using Low Doses in a Small Sample of Women with Chronic Posttraumatic Stress Disorder

Abstract The purpose of this study was to investigate the safety of different doses of MDMA-assisted psychotherapy administered in a psychotherapeutic setting to women with chronic PTSD secondary to a sexual assault, and also to obtain preliminary data regarding efficacy. Although this study was originally planned to include 29 subjects, political pressures led to the closing of the study before it could be finished, at which time only six subjects had been treated. Preliminary results from those six subjects are presented here. We found that low doses of MDMA (between 50 and 75 mg) were both psychologically and physiologically safe for all the subjects. Future studies in larger samples and using larger doses are needed in order to further clarify the safety and efficacy of MDMA in the clinical setting in subjects with PTSD.

Common basal extrastriate areas for the semantic processing of words and pictures.

OBJECTIVE The recognition potential (RP) is an electrophysiological brain response which is sensitive to the semantic processing of meaningful stimuli. In this study we attempt to elucidate the topography and neural origin of the RP evoked by pictures and to compare it with the RP evoked by words. METHODS Words, pictures, Chinese characters and control stimuli were presented to 20 subjects following the rapid stream stimulation procedure. The activity was recorded using 60 cephalic electrodes. RESULTS We found a RP displaying its maximal amplitude at the left inferior parieto-occipital electrode (PO7) for words and at the right homologue electrode (PO8) for pictures and Chinese characters. Both the amplitude and the latency of the RP were larger in the case of words. A profile analysis indicated that the neural generators of the RP were common regardless of the type of stimulus, and a dipole analysis placed them about the lingual gyrus. CONCLUSIONS Words and pictures share the same neural generators for the RP despite of subtle differences in lateralization. This is interpreted as an index of a multimodal semantic processing in basal extrastriate areas.

Human brain potentials of spatial location encoding into memory

Event-related potentials (ERP) were elicited by little vertical bars located randomly in 1 of 4 positions (top, bottom, left or right) relative to a central fixation point. There were 4 experimental conditions requiring the subjects either to press a button if the stimulus was in the target location, count the number of stimuli appearing in the target location, look at the stimuli passively or memorize the location of the stimulus. The interstimulus interval was 2 sec for all tasks. In the memory condition subjects had to consider stimuli as pairs, memorize the location of the first stimulus of every pair and press a button if the second stimulus was in the same location. Our results indicate that ERPs corresponding to the memorization and retention of spatial location are different from those of the other 3 tasks in the presence of a long duration negativity mainly distributed bilaterally over O1, O2, T5 and T6 electrodes. This negativity seems to develop gradually several milliseconds before stimulus onset, reaches its highest value when the spatial location is assumed to be analyzed, and continues with uniform scalp distribution until the end of the recording (822 msec after stimulus onset).

Working Memory Within The Visual Dorsal Stream: Brain Potentials of Spatial Location and Motion Direction Encoding Into Memory

Recently, evidence of two different working memory subsystems for visual information has been found, these subsystems corresponding to the two main visual pathways: the dorsal stream for motion-spatial information and the ventral stream for object information. This study aimed further to dissociate different working memory subsystems within one of the streams, namely within the dorsal stream. For these purposes, event-related potentials (ERP) were recorded while subjects memorized either the spatial location or the motion direction of stimuli. These ERPs were compared to ERPs recorded while subjects looked at the same stimuli but performed other control, nonmemory tasks. Results revealed an important difference in ERP modulation between a working memory subsystem for spatial location and another subsystem for motion direction, providing evidence of different working memory subsystems within the dorsal stream.