Mario Rodríguez-Camacho

Involuntary attention impairment in early Parkinson's disease: An event-related potential study

Dopaminergic nigro-striatal depletion interferes with the detection of novel stimuli. This suggests that Parkinsons disease (PD) may generate from the initial stages a failure in involuntary attention (IA), which can be studied through the distraction potential, composed by the mismatch negativity (MMN), the P3a and the reorientation negativity (RON). This study analyzed IA using event-related potentials (ERPs) in patients with early PD with and without dopaminergic replacement therapy. Twenty-five medicated, and 17 non-medicated patients with early PD were studied, as well as 20 healthy control subjects. All subjects performed an auditory distraction task while a digital EEG was being recorded. The distraction potential was obtained by averaging methodology. Each wave was analyzed with a Repeated Measures ANOVA test. The MMN was obtained in all subjects and no significant differences in mean amplitude were found among the groups. There was a main effect of group for the amplitude of P3a (F(2,59)=4.8, p=0.01, ɛ=0.411), with a significant lower amplitude in the medicated group compared to the control group (MD=-1.03, p=0.003). RON also showed a main effect of group (F(2,59)=4.8, p=0.01, ɛ=0.467), with significantly lower amplitudes in non-medicated patients with respect to both the control and medicated groups (MD=1.19, p=0.01, MD=1.27, p=0.005, respectively). There were no significant differences in the latencies of any of the waves among the groups. The main finding of this study was the reduction in the IA in early PD. Reorientation of attention (RON) showed a dopaminergic modulation in these patients. These results represent the basis for future in depth studies on the involvement of IA in executive impairments in PD.

Event-related potentials findings differ between children and adults during arithmetic-fact retrieval

Some cognitive abilities of arithmetical calculation depend on retrieval of arithmetic facts from long-term memory. Arithmetic-fact retrieval has been studied in adults through Event-Related Potentials (ERP) experiments. Such information in children, however, has been scarce. It has been reported that from the age of 9 years, children employ a memory retrieval strategy for solving simple multiplication problems. The present study compared arithmetical-fact retrieval in children and adults while they were being subjected to ERP recording. The subjects were asked to make judgments about solutions to simple multiplication problems. Both groups of participants displayed the so-called arithmetic N400 effect for incorrect solutions relative to correct solutions. Adults showed a posterior N400 effect, while children showed a widely distributed N400 effect. Children displayed a larger amplitude and longer latency arithmetic N400 component than adults; this observation could be due to children exerting greater effort involving more widespread cortical activation than adults to solve the experimental problems. The Late Positive Component (LPC), which follows the arithmetic N400 and has been described previously in adult subjects, was observed in the present adult subjects, but was present in children only for correct solutions. These results may indicate that, relative to adults, children showed slower memory retrieval and a different pattern of a verification mechanism for correct and incorrect solutions.

Poor reading skills may involve a failure to focus attention

A source localization analysis was carried out to provide brain functional and structural assessments of individuals with poor reading skills. Standardized low-resolution brain electromagnetic tomography was used to locate sources of P2 and P3 event-related potential components in normal readers and in poor reader children performing a cued continuous performance task. Cue-elicited P2 sources in the right superior parietal gyrus were smaller in 37 poor readers than in 40 normal readers. Poor readers showed a higher P3 activation in response to a false target in frontal and frontorbital regions than normal readers. These results suggest that reading disabilities may be attributed to failures in attentional focalization for incoming stimuli.

Semantic Processing Impairment in Patients with Temporal Lobe Epilepsy.

The impairment in episodic memory system is the best-known cognitive deficit in patients with temporal lobe epilepsy (TLE). Recent studies have shown evidence of semantic disorders, but they have been less studied than episodic memory. The semantic dysfunction in TLE has various cognitive manifestations, such as the presence of language disorders characterized by defects in naming, verbal fluency, or remote semantic information retrieval, which affects the ability of patients to interact with their surroundings. This paper is a review of recent research about the consequences of TLE on semantic processing, considering neuropsychological, electrophysiological, and neuroimaging findings, as well as the functional role of the hippocampus in semantic processing. The evidence from these studies shows disturbance of semantic memory in patients with TLE and supports the theory of declarative memory of the hippocampus. Functional neuroimaging studies show an inefficient compensatory functional reorganization of semantic networks and electrophysiological studies show a lack of N400 effect that could indicate that the deficit in semantic processing in patients with TLE could be due to a failure in the mechanisms of automatic access to lexicon.

Event-Related Brain Potentials during a Semantic Priming Task in Children with Learning Disabilities Not Otherwise Specified

Learning disabilities (LDs) are the most common psychiatric disorders in children. LDs are classified either as “Specific” or “Learning Disorder Not Otherwise Specified”. An important hypothesis suggests a failure in general domain process (i.e., attention) that explains global academic deficiencies. The aim of this study was to evaluate event-related potential (ERP) patterns of LD Not Otherwise Specified children with respect to a control group. Forty-one children (8−10.6 years old) participated and performed a semantic judgment priming task while ERPs were recorded. Twenty-one LD children had significantly lower scores in all academic skills (reading, writing and arithmetic) than twenty controls. Different ERP patterns were observed for each group. Control group showed smaller amplitudes of an anterior P200 for unrelated than related word pairs. This P200 effect was followed by a significant early N400a effect (greater amplitudes for unrelated than related word pairs; 350–550 ms) with a right topographical distribution. By contrast, LD Not Otherwise Specified group did not show a P200 effect or a significant N400a effect. This evidence suggests that LD Not Otherwise Specified children might be deficient in reading, writing and arithmetic domains because of their sluggish shifting of attention to process the incoming information.

Visuospatial Working Memory in Toddlers with a History of Periventricular Leukomalacia: An EEG Narrow-Band Power Analysis

Background Periventricular Leukomalacia (PVL) affects white matter, but grey matter injuries have also been reported, particularly in the dorsomedial nucleus and the cortex. Both structures have been related to working memory (WM) processes. The aim of this study was to compare behavioral performances and EEG power spectra during a visuospatial working memory task (VSWMT) of toddlers with a history of PVL and healthy toddlers. Methodology/Principal Findings A prospective, comparative study of WM was conducted in toddlers with a history of PVL and healthy toddlers. The task responses and the EEG narrow-band power spectra during a VSWMT were compared in both groups. The EEG absolute power was analyzed during the following three conditions: baseline, attention and WM retention. The number of correct responses was higher in the healthy group (20.5±5.0) compared to the PVL group (16.1±3.9) (p = 0.04). The healthy group had absolute power EEG increases (p≤0.05) during WM compared to the attention condition in the bilateral frontal and right temporal, parietal and occipital regions in frequencies ranging from 1.17 to 2.34 Hz and in the right temporal, parietal and occipital regions in frequencies ranging from 14.06 to 15.23 Hz. In contrast, the PVL group had absolute power increases (p≤0.05) in the bilateral fronto-parietal, left central and occipital regions in frequencies that ranged from 1.17 to 3.52 Hz and in the bilateral frontal and right temporal regions in frequencies ranging from 9.37 to 19.14 Hz. Conclusions/Significance This study provides evidence that PVL toddlers have visuospatial WM deficits and a very different pattern of absolute power increases compared to a healthy group of toddlers, with greater absolute power in the low frequency range and widespread neuronal networks in the WM retention phase.

Phonological processing in Parkinson's disease: a neuropsychological assessment.

Patients with Parkinson’s disease (PD) have cognitive deficits that cause functional impairments across several domains, including language. There is experimental evidence that basal ganglia and frontostriatal circuits are implicated in phonological processing, which leads to the hypothesis that a dysfunction of these circuits could be expressed behaviorally as phonological deficiencies in patients with PD. Using neuropsychological assessments, the present study aimed to explore the phonological processing abilities of patients in the initial stages of PD while controlling for other cognitive processes. The results showed lower scores in patients with PD on phonological tests with respect to a control group and these differences were independent of processes such as attention/working memory, long-term memory, thinking, and verbal language comprehension. However, there was an association between phonological skills and reading comprehension abilities. This finding implies a specific phonological deficit in terms of word reading.

Effects of age and working memory load on syntactic processing: an event-related potential study

Cognitive changes in aging include working memory (WM) decline, which may hamper language comprehension. An increase in WM demands in older adults would probably provoke a poorer sentence processing performance in this age group. A way to increase the WM load is to separate two lexical units in an agreement relation (i.e., adjective and noun), in a given sentence. To test this hypothesis, event-related potentials (ERPs) were collected from Spanish speakers (30 older adults, mean age = 66.06 years old; and 30 young adults, mean age = 25.7 years old) who read sentences to detect grammatical errors. The sentences varied with regard to (1) the gender agreement of the noun and adjective, where the gender of the adjective either agreed or disagreed with the noun, and (2) the WM load (i.e., the number of words between the noun and adjective in the sentence). No significant behavioral differences between groups were observed in the accuracy of the response, but older adults showed longer reaction times regardless of WM load condition. Compared with young participants, older adults showed a different pattern of ERP components characterized by smaller amplitudes of LAN, P600a, and P600b effects when the WM load was increased. A smaller LAN effect probably reflects greater difficulties in processing the morpho-syntactic features of the sentence, while smaller P600a and P600b effects could be related to difficulties in recovering and mapping all sentence constituents. We concluded that the ERP pattern in older adults showed subtle problems in syntactic processing when the WM load was increased, which was not sufficient to affect response accuracy but was only observed to result in a longer reaction time.