Characterization of the Sensorimotor Rhythm in 4-Month-Old Infants Born at Term and Premature.

The sensorimotor rhythm (SMR) is an electroencephalographic rhythm associated with motor and cognitive development observed in the central brain regions during wakefulness in the absence of movement, and it reacts contralaterally to generalized and hemibody movements. The purpose of this work was to characterize the SMR of 4-month-old infants, born either healthy at term or prematurely with periventricular leukomalacia (PVL). Two groups of infants were formed: healthy and premature with PVL. Their electroencephalograms (EEGs) were recorded in four conditions: rest, free movement, right-hand grasping and left-hand grasping, in order to explore general reactivity to free movement and contralateral reactivity in hand-grasping conditions. Associations between SMR, and cognitive and motor performance were analyzed. The healthy infants showed a SMR between 5.47 and 7.03 Hz, with clear contralateral reactivity to free movement and right-hand grasping. However, the premature infants with PVL did not show enough electroencephalographic characteristics to evidence the presence of SMR. Poor performance, characteristic of children with PVL, was related to low-frequency SMR, while good performance was associated with a higher frequency rhythm in the left hemisphere. The presence of SMR in the group of healthy infants could be considered a sign of health at this age. Thus, poor SMR evidence in the EEG of infants with PVL is probably a sign of brain immaturity or brain dysfunction. Our results provide data on infant SMR development that is needed to design neurofeedback protocols for infants with PVL.

Neurofeedback in Learning Disabled Children: Visual versus Auditory Reinforcement.

Children with learning disabilities (LD) frequently have an EEG characterized by an excess of theta and a deficit of alpha activities. NFB using an auditory stimulus as reinforcer has proven to be a useful tool to treat LD children by positively reinforcing decreases of the theta/alpha ratio. The aim of the present study was to optimize the NFB procedure by comparing the efficacy of visual (with eyes open) versus auditory (with eyes closed) reinforcers. Twenty LD children with an abnormally high theta/alpha ratio were randomly assigned to the Auditory or the Visual group, where a 500 Hz tone or a visual stimulus (a white square), respectively, was used as a positive reinforcer when the value of the theta/alpha ratio was reduced. Both groups had signs consistent with EEG maturation, but only the Auditory Group showed behavioral/cognitive improvements. In conclusion, the auditory reinforcer was more efficacious in reducing the theta/alpha ratio, and it improved the cognitive abilities more than the visual reinforcer.

Cross-modal plasticity in Cuban visually-impaired child cochlear implant candidates: topography of somatosensory evoked potentials.

INTRODUCTION: Studies of neuroplasticity have shown that the brain's neural networks change in the absence of sensory input such as hearing or vision. However, little is known about what happens when both sensory modalities are lost (deaf-blindness). Hence, this study of cortical reorganization in visually-impaired child cochlear implant (CI) candidates. OBJECTIVE: Assess cross-modal plasticity, specifically cortical reorganization for tactile representation in visually-impaired child CI candidates, through study of topography of somatosensory evoked potentials (SEP). METHODS: From April through September 2005, SEP from median and tibial nerve electrical stimulation were studied in 12 visually-impaired child CI candidates aged 3-15 years and 23 healthy controls. Following placement of 19 recording electrodes using the International 10-20 System , SEP were recorded and then processed. Topographic maps were obtained for SEP N20 (median nerve) and SEP P40 (tibial nerve), permitting assessment of cortical reorganization by comparing visually-impaired, deaf children's maps with those of healthy children by means of visual inspection and statistical comparison using a permutation test. RESULTS: SEP N20 topography was significantly more extensive in visually-impaired child CI candidates than in healthy children. An asymmetrical pattern occurred from the expansion of hand tactile activation into the temporal and occipital regions in the left hemisphere on right median nerve stimulation. This did not occur for SEP P40 on tibial nerve stimulation (right and left). Magnitude of expanded SEP N20 response was related to severity of visual impairment and longer duration of dual sensory loss. CONCLUSIONS: Changes in SEP N20 topography are evidence of cross-modal plasticity in visually-impaired child CI candidates, appearing to result from a complex interaction between severity of visual impairment and duration of multisensory deprivation.

Neurofeedback in healthy elderly human subjects with electroencephalographic risk for cognitive disorder.

In normal elderly subjects, the best electroencephalogram (EEG)-based predictor of cognitive impairment is theta EEG activity abnormally high for their age. The goal of this work was to explore the effectiveness of a neurofeedback (NFB) protocol in reducing theta EEG activity in normal elderly subjects who present abnormally high theta absolute power (AP). Fourteen subjects were randomly assigned to either the experimental group or the control group; the experimental group received a reward (tone of 1000 Hz) when the theta AP was reduced, and the control group received a placebo treatment, a random administration of the same tone. The results show that the experimental group exhibits greater improvement in EEG and behavioral measures. However, subjects of the control group also show improved EEG values and in memory, which may be attributed to a placebo effect. However, the effect of the NFB treatment was clear in the EG, although a placebo effect may also have been present.

Changes in EEG current sources induced by neurofeedback in learning disabled children. An exploratory study.

The objective of this work was to explore Neurofeedback (NFB) effects on EEG current sources in Learning Disabled (LD) children, and to corroborate its beneficial consequences on behavioral and cognitive performance. NFB was given in twenty 30-min sessions to 11 LD children to reduce their abnormally high theta/alpha ratios (Experimental Group). Another five LD children with the same characteristics received a placebo treatment (Control Group). In the Control Group no changes in behavior or EEG current source were observed. In the Experimental Group, immediately after treatment children showed behavioral and cognitive improvements, but current source analysis showed few modifications; however, 2 months after treatment many changes occurred: a decrease in current of frequencies within the theta band, mainly in left frontal and cingulate regions, and enhancement in current of frequencies within the alpha band, principally in the right temporal lobe and right frontal regions, and of frequencies within the beta band, mainly in left temporal, right frontal and cingulate cortex regions. In conclusion, NFB is a possibly efficacious treatment for LD children with an abnormally high theta/alpha ratio in any lead. The changes observed in EEG current sources may reflect the neurophysiological bases of the improvement that children experienced in their behavioral and cognitive activities.

Specific EEG frequencies signal general common cognitive processes as well as specific task processes in man.

The EEG of 10 normal male young adults was recorded during the performance of three different tasks: mental calculation, verbal working memory (VWM) and spatial working memory (SWM). The stimuli used in the three tasks were the same, only the instructions to the subjects were different. Narrow band analysis of the EEG and distributed sources for each EEG frequency were calculated using variable resolution electromagnetic tomography (VARETA). At some frequencies (1.56, 4.68, 7.80 to 10.92 Hz) at least two tasks produced similar EEG patterns that were interpreted as the reflex of common cognitive processes, such as attention, inhibition of irrelevant stimuli, etc. Specific changes were also observed at 2.34, 3.12, 3.90, 5.46 and 6.24 Hz. The first three of these frequencies showed similar changes during VWM and calculus at the left frontal cortex, suggesting the activation of working memory (WM) processes. The interaction effect at these frequencies was mainly observed at the anterior cingulate cortex and frontal cortex. At 5.46 and 6.24 Hz, changes were only observed during mental calculation.

Are poor readers semantically challenged? An event-related brain potential assessment.

This study explores visual event-related potentials components in a group of poor readers (PRs) and control children who carried out figure and word categorization tasks. In both tasks, every child had to categorize between animal and non-animal stimuli in an odd-ball GO-GO paradigm. During the word categorization task, PRs presented longer reaction times, a poorer performance, longer and larger P2 amplitudes, and smaller amplitudes and longer P300 latencies than controls. There were no differences in the N400 component between groups. These results suggest that semantic processing underachievement in PRs may not be a semantic deficit per se, but the late reflection of an early word codification problem, deficient use of attentional resources and lack of target identification during reading.

Covert matching of unfamiliar faces in a case of prosopagnosia: an ERP study.

In addition to their deficit in overt face recognition, patients with prosopagnosia also have difficulties in matching sequentially presented unfamiliar faces. Here we assessed the possibility that covert matching of faces was present in a case with prosopagnosia using event-related potentials (ERPs). The participants (patient FE and normal controls) were challenged with a face-identity matching task, in which they decided whether two sequentially presented photographs of unfamiliar faces represented the same person. Only internal face features were used and the two faces in a pair differed in emotional expression. FE failed to overtly match these stimuli. In contrast, the ERPs revealed evidence of covert matching. If the two faces within a pair of stimuli depicted different posers, then the response to the second face contained an enhanced N300 compared to the situation where the identity of the faces was the same. The latency of the N300 was the same as a similar component found in controls. These results suggest that some cases with prosopagnosia have a covert ability to match unfamiliar faces, with similar temporal dynamics as controls, which in contrast with the idea that a generalized slowing of face processing occurs in all cases of prosopagnosia.