Cláudio Elidio Portella

Alzheimer's disease and implicit memory

Specific neuropsychiatric disorders, such as Alzheimers disease (AD) affect some forms of memory while leaving others relatively intact. In this review, we investigate particularities of the relationship between explicit and implicit memories in AD. It was found that implicit memory is preserved in AD, irrespective of the task used; in other words, there was not interference from explicit memory. In addition, it was verified that is possible through implicit memory compensatory strategies such as, activities of daily living (ADL) to compensate for the explicit memory deficits. In this sense, cognitive rehabilitation (CR) demonstrates reasonable results in the process of compensation of explicit memory deficits. Concluding, the decline in explicit memory suggests that both systems are functionally independent even if the other is compromised. We expect that when explicit memory system is not involved in competition with the implicit system, the final effect of learning is better, because all of the implicit memory capacity is engaged in learning and not in competition with the explicit system.

Electrophysiological analysis of a sensorimotor integration task

The present experiment aimed at investigating electrophysiologic changes observed as beta band asymmetry, by Quantitative Electroencephalography (qEEG), when individuals performed a reaching motor task (catching a ball in free fall). The sample was composed of 23 healthy individuals, of both sexes, with ages varying between 25 and 40 years old. All the subjects were right handed. A two-way ANOVA was applied for the statistical analysis, to verify the interaction between task moment (i.e., 2s before and 2s after balls fall) and electrode (i.e., frontal, central and temporal regions). The first analysis compared electrodes placed over the somatosensory cortex. Central sites (C3-C4) were compared with temporal regions (T3-T4). The results showed a main effect for moment and position. The second analysis was focused over the premotor cortex, which was represented by the electrodes placed on the frontal sites (F3-F4 versus F7-F8), and a main effect was observed for position. Taken together, these results show a pattern of asymmetry in the somatosensory cortex, associated with a preparatory mechanism when individuals have to catch an object during free fall. With respect to task moment, after the balls fall, the asymmetry was reduced. Moreover, the difference in asymmetry between the observed regions were related to a supposed specialization of areas (i.e., temporal and central). The temporal region was associated with cognitive processes involved in the motor action (i.e., explicit knowledge). On the other hand, the central sites were related to the motor control mechanisms per se (i.e., implicit knowledge). The premotor cortex, represented by two frontal regions (i.e., F3-F4 versus F7-F8), showed a decrease on neural activity in the contralateral hemisphere (i.e., to the right hand). This result is in agreement with other experiments suggesting a participation of the frontal cortex in the planning of the apprehension task. This sensorimotor paradigm may contribute to the repertoire of tasks used to study clinical conditions such as depression, alzheimer and Parkinson diseases.

Relationship between early and late stages of information processing: an event-related potential study

The brain is capable of elaborating and executing different stages of information processing. However, exactly how these stages are processed in the brain remains largely unknown. This study aimed to analyze the possible correlation between early and late stages of information processing by assessing the latency to, and amplitude of, early and late event-related potential (ERP) components, including P200, N200, premotor potential (PMP) and P300, in healthy participants in the context of a visual oddball paradigm. We found a moderate positive correlation among the latency of P200 (electrode O2), N200 (electrode O2), PMP (electrode C3), P300 (electrode PZ) and the reaction time (RT). In addition, moderate negative correlation between the amplitude of P200 and the latencies of N200 (electrode O2), PMP (electrode C3), P300 (electrode PZ) was found. Therefore, we propose that if the secondary processing of visual input (P200 latency) occurs faster, the following will also happen sooner: discrimination and classification process of this input (N200 latency), motor response processing (PMP latency), reorganization of attention and working memory update (P300 latency), and RT. N200, PMP, and P300 latencies are also anticipated when higher activation level of occipital areas involved in the secondary processing of visual input rise (P200 amplitude).

EEG SPECTRAL COHERENCE INTER AND INTRAHEMISPHERIC DURING CATCHING OBJECT FALL TASK

The aim of the present study was to evaluate coherence measures at Theta through qEEG during the accomplishment of a specific motor task. The sample consisted of 23 healthy individuals, both sexes, with ages varying between 25 and 40 years old. All subjects were submitted to a specific motor task of catching sequences of falling balls. A three-way ANOVA was employed for the statistical analysis, which demonstrated main effects for the following factors: time, block and position. However, there was no interaction between the factors. A significant and generalized coherence reduction was observed during the task execution time. Coherence was also diminished at the left frontal cortex and contralateral hemisphere of the utilizing limb (comparing to the right frontal cortex). In conclusion, these findings suggest a certain specialization of the neural circuit, also according to previous investigations. The inter-coherence reduction suggests a spatial inter-electrode dependence during the task, rather than a neuronal specialization.

Medidas eletrencefalográficas durante a aprendizagem de tarefa motora sob efeito do bromazepam

Neuromodulators change brains neural circuitry. Bromazepam is often been used in the pharmacological treatment of anxiety disorders. Few papers links this anxiolytic to motor tasks. The purpose of this study was to examine motor and electrophysiological changes produced by administration of bromazepam in differents doses (3 and 6 mg). The sample consisted of 39 healthy individuals, of both sexes, between 20 and 30 years of age. The control (placebo) and experimental (bromazepam 3mg and bromazepam 6 mg) groups were submitted to a typewriting task, in a randomized, double-blind design. The results did not reveal differences on score and time of the attention test. In the comportamental analysis was noticed blocks as main effect to behavioral variables (time and mistakes in the task). Electrophysiological data showed significants interactions to: laterally/condition/moment; laterally/condition; laterally/moment; condition/moment; condition/site.

Changes in quantitative EEG absolute power during the task of catching an object in free fall.

The aim of this study was to verify changes in absolute power (qEEG), in theta, during the catch of a free falling object. The sample consisted of 10 healthy individuals, of both genders, with ages between 25 and 40 years. A three-way ANOVA followed by Post-Hoc analysis was applied. The results demonstrated main effects for time and position. In conclusion, a motor task that involves expectation produces deactivation of non-relevant areas in the ipsilateral hemisphere of the active limb. On the other hand, the patterns of results showed activation in areas responsible for planning and selection of motor repertoires in the contralateral hemisphere.

Aprendizagem de procedimentos e efeitos ansiolíticos: medidas eletrencefalográficas, motora e atencional

The objective of the present study was to evaluate attentional, motor and electroencephalographic (EEG) parameters during a procedural task when subjects have ingested 6mg of bromazepam. The sample consisted of 26 healthy subjects, male or female, between 19 and 36 years of age. The control (placebo) and experimental (bromazepam 6mg) groups were submitted to a typewriting task in a randomized, double-blind design. The findings did not show significant differences in attentional and motor measures between groups. Coherence measures (qEEG) were evaluated between scalp regions, in theta, alpha and beta bands. A first analysis revealed a main effect for condition (Anova-2way - condition versus blocks). A second Anova 2-way (condition versus scalp regions) showed a main effect for both factors. The coherence measure was not a sensitive tool at demonstrating differences between cortical areas as a function of procedural learning.

Integration of cortical areas during performance of a catching ball task

The study aimed to elucidate electrophysiological and cortical mechanisms involved in anticipatory actions when healthy subjects had to catch balls in free drop; specifically through quantitative electroencephalography (qEEG) alpha absolute power changes. Our hypothesis is that during the preparation of motor action (i.e., 2s before balls drop) occurred integration among left medial frontal, left primary somatomotor and left posterior parietal cortices, showing a differentiated activity involving expectation, planning and preparedness. This hypothesis supports a lateralization of motor function. Although we contend that in right-handers the left hemisphere takes on a dominant role for the regulation of motor behavior. The sample was composed of 23 healthy subjects (13 male and 10 female), right handed, with ages varying between 25 and 40 years old (32.5+/-7.5), absence of mental and physical illness, right handed, and do not make use of any psychoactive or psychotropic substance at the time of the study. The experiment consisted of a task of catching balls in free drop. The three-way ANOVA analysis demonstrated an interaction between moment and position in left medial frontal cortex (F3 electrode), somatomotor cortex (C3 electrode) and posterior parietal cortex (P3 electrode; p < 0.001). Summarizing, through experimental task employed, it was possible to observe integration among frontal, central and parietal regions. This integration appears to be more predominant in expectation, planning and motor preparation. In this way, it established an absolute predominance of this mechanism under the left hemisphere.

Coerência espectral do eletrencefalograma em pacientes submetidos a transposição tendinosa: estudo pré e pós-operatório

Tendon transfer of the tibiliais posterior muscle is a surgical intervention widely employed in orthopedics for the correction of drop foot caused by leprosy. However, few models have proposed a thorough investigation of the brain plasticity phenomenon during tendon transfer. Thus, the present study aimed at analyzing EEG spectral coherence (SC) in patients submitted to tendon transfer of the tibiliais posterior muscle by Srinivasans technique and quantitative EEG (EEGq). The sample consisted of four subjects with drop foot caused by leprosy. The SC parameter was evaluated in two experimental moments: pre and post-surgery. Results demonstrated a main moment effect for the C3-CZ electrode pair. Specifically, a significant increase in coherence values was observed. However, the ANOVA did not indicate a significant band/moment interaction. It can be assumed that coherence augmentation indicates that functional rehabilitation promoted by this specific surgery yields cortical alterations.

Changes in cortical relative power in patients submitted to a tendon transfer: a pre and post surgery study

The aim of this study is analyze possible modifications in the cerebral cortex, through quantitative electroencephalography (qEEG) in patients submitted to a tendon transfer procedure (posterior tibialis) by the Srinivasans technique. Four subjects (2 men and 2 women), 49.25 age average (SD +/ 21.4) were studied. All subjects have been through surgical procedure due to leprosy and had, at least, two years of drop foot condition. The qEEG measured the electrocortical activity (relative power) between 8 and 25 Hz frequencies pre and post surgery. A paired t test analyzed all data (p< or =0,05). The results show significant alterations in the alpha relative power, electrodes F7 (p=0.01) and F8 (p=0.021). Altogether, based on findings of the current literature, we can conclude that the tendon transfer procedure suggests electrocortical alterations sensitive to specific qEEG bands.