Tomás Ortiz Alonso

P300 latency and amplitude in the diagnosis of dementia

P300 latency and amplitude were investigated in 10 normal elderly individuals, 10 institutionalized elderly persons with dementia not of the Alzheimers types, and 10 elderly people with Alzheimers disease. Significant differences between control and dementia groups (but not between dementia groups) were noted in the P300 latency, but not amplitude. Such differential latencies were observed in the anterior and in the left temporal and parietal areas of the brain.

MEG resting-state differences as a marker of clinical subtype in schizophrenia

A resting-state magnetoencephalography (MEG) can discriminate different subtypes of schizophrenia. We studied a sample of 45 male patients (age range was 27 to 55 years old) with schizophrenia diagnosis from San Juan de Dios Hospital (Ciempozuelos, Madrid, Spain) equally distributed among paranoid (n=15), residual (n=15) and disorganized (n=15) subtypes according to the Structured Clinical Interview for DSM-III-R Axis I Disorders (SCID-I). Healthy controls (N=20) are males, matched by age and sex at the Magnetoencefalografie Center “Dr. Perez-Modrego” (Madrid, Spain), without current or past neurological and/or psychiatric illness of any sort, including substance abuse. When we estimated the ability of the predominant symptom dimensions to segregate the resting MEG amplitude profiles using canonical discriminant analysis, three discriminant functions DF) were extracted, explaining 52% (χ2=584.291, p<0.000), 25% (χ2=323.354, p=0.115) and 22% (χ2=155.037, p=0.289) of the total variance respectively. Our findings are consistent with the idea that clinical dimensions of schizophrenia derived from the predominant clinical syndrome are an expression of specific dysfunction of the brain subsystems of the default network.

Differences in Early Stages of Tactile ERP Temporal Sequence (P100) in Cortical Organization during Passive Tactile Stimulation in Children with Blindness and Controls

Compared to their seeing counterparts, people with blindness have a greater tactile capacity. Differences in the physiology of object recognition between people with blindness and seeing people have been well documented, but not when tactile stimuli require semantic processing. We used a passive vibrotactile device to focus on the differences in spatial brain processing evaluated with event related potentials (ERP) in children with blindness (n = 12) vs. normally seeing children (n = 12), when learning a simple spatial task (lines with different orientations) or a task involving recognition of letters, to describe the early stages of its temporal sequence (from 80 to 220 msec) and to search for evidence of multi-modal cortical organization. We analysed the P100 of the ERP. Children with blindness showed earlier latencies for cognitive (perceptual) event related potentials, shorter reaction times, and (paradoxically) worse ability to identify the spatial direction of the stimulus. On the other hand, they are equally proficient in recognizing stimuli with semantic content (letters). The last observation is consistent with the role of P100 on somatosensory-based recognition of complex forms. The cortical differences between seeing control and blind groups, during spatial tactile discrimination, are associated with activation in visual pathway (occipital) and task-related association (temporal and frontal) areas. The present results show that early processing of tactile stimulation conveying cross modal information differs in children with blindness or with normal vision.