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Cognitive impairment in amyotrophic lateral sclerosis: evidence from neuropsychological investigation and event-related potentials

The presence of subclinical cognitive impairment in patients with amyotrophic lateral sclerosis (ALS) is investigated using neuropsychological assessment and event-related potential recordings (ERP). An extensive battery of neuropsychological tests assessing the domains of attention, memory, language, visuo-spatial and executive functions were administered to 20 non-demented patients with sporadic ALS and 13 age- and education-matched healthy control subjects. Mismatch negativity (MMN), P3b, P3a (novelty P300) and contingent negative variation (CNV) were recorded. ALS patients were significantly impaired in tests of working memory, sustained attention, response inhibition, naming, verbal fluency and complex visuo-spatial processing. The memory impairment seemed to be secondary to deficits in forming learning strategies and retrieval. In ERP recordings, P3a and P3b amplitudes of ALS patients were lower compared with the controls, P3a latencies were significantly longer and mean CNV amplitudes were higher. These results indicate subclinical impairment of cognitive functions in patients with ALS. The pattern of cognitive impairment suggests the dysfunction of the frontal network.

Effects of cold stress on early and late stimulus gating.

The P50 component of the event-related potential (ERP) mainly reflects early pre-attentional processing. Along with P50, the N100 component and mismatch negativity (MMN) were postulated to represent a complex multistage and multi-component gating system. If some variable threshold or gating is exceeded by the MMN signal, the MMN is often followed by a relatively sharp fronto-central positive wave, the P3a component, which reflects an attentional switch to an environmental change. The P50 was shown to be affected by mental and cold stress, and the P3a amplitude was shown to be increased by the anticipation of threat. The aim of this study is to examine concurrently the early and late ERP indices of gating during acute stress. The ERPs to auditory stimuli in a passive oddball paradigm were recorded in 15 normal subjects during the cold pressor test and a control condition. The cold pressor test diminished P50 gating, increased N100 amplitude, elicited P3a responses and had no significant effect on MMN. Transient stress could impair early sensory gating and the ability to ignore irrelevant information that can cause passive attention switches indexed by the P3a component.

Human Auditory Fast and Slow Omitted Stimulus Potentials and Steady-State Responses

Two kinds of omitted stimulus potentials (OSP) are called “fast” and “slow.” Fast OSPs, recently found with visual stimuli, are here extended to auditory; they occur after omissions or after the end of trains of 1 to > 20 Hz clicks. Slow OSPs, long known, follow trains of 0.3 to 4 Hz. Each has its constant peak latency after the due-time of the first missing stimulus, as though the system is expecting something quite accurately on schedule. They differ in dynamics and slow OSPs require the subject to attend; fast OSPs do not. Steady-state responses (SSR) at a critical click rate of 6–7 Hz sometimes appear to alternate between two forms and OSPs may depend on which they follow. Fast OSPs can occur to the first, second and even the third omissions after the end of a train. Short conditioning periods suffice. Irregular interstimulus intervals do not reduce fast OSPs but attenuate slow OSPs.

The Morpho-functional Evaluation of Retina in Amblyopia

Abstract Purpose: To investigate the morphological or functional differences of retina in amblyopia. Materials and methods: Forty-one patients with unilateral strabismic, anisometropic or combined amblyopia were included in the study. A control group was composed of 16 normal children. All participants were tested with optical coherence tomography (OCT) and pattern electroretinography (PERG). The findings from amblyopic and nonamblyopic eyes were compared among the amblyopic groups. Also, amblyopic and nonamblyopic eyes were compared with the healthy control eyes. Results: No significant difference was found in OCT parameters for amblyopic and nonamblyopic eyes among the amblyopic groups (p > 0.05). In the combined and anisometropic groups, ganglion cell complex (GCC) was found to be significantly increased in both amblyopic and nonamblyopic eyes compared to the control group (p < 0.05). In strabismic amblyopia, significant reduction in GCC thickness and increase in foveal thickness were found, compared to nonamblyopic eyes (p = 0.019, p = 0.08). There were no significant differences in PERG amplitude and latency between the amblyopic and the nonamblyopic eyes in amblyopic groups (p > 0.05). PERG amplitude in amblyopic eyes was found to be significantly decreased compared with that in normal eyes (p < 0.05). When the nonamblyopic eyes were compared with the control group, only the anisometropic amblyopia group demonstrated significant reduction in amplitude and prolongation in latency (p = 0.002, p = 0.026). Conclusion: We found no significant differences in morphological and functional measures among amblyopic groups. However, we detected significant differences in the retinal function and morphology of both amblyopic and nonamblyopic eyes compared with healthy control eyes.

The effects of interstimulus interval on sensory gating and on preattentive auditory memory in the oddball paradigm. Can magnitude of the sensory gating affect preattentive auditory comparison process

P50, and mismatch negativity (MMN) are components of event-related potentials (ERP) reflecting sensory gating and preattentive auditory memory, respectively. Interstimulus interval (ISI) is an important determinant of the amplitudes of these components and N1. In the present study the interrelation between stimulus gating and preattentive auditory sensory memory were investigated as a function of ISI in 1.5, 2.5 and 3.5s in 15 healthy volunteered participants. ISI factor affected the N1 peak amplitude significantly. MMN amplitude in 2.5s ISI was significantly smaller compared to 1.5 and 3.5s ISI. ISI X stimuli interaction on P50 amplitude was statistically significant. P50 amplitudes to deviant stimuli in 2.5s ISI were larger than the P50 amplitudes in other ISIs. P50 difference (P50d) waveform amplitude correlated significantly with MMN amplitude. The results suggest that: (i) auditory sensory gating could affect preattentive auditory sensory memory by supplying input to the comparator mechanism; (ii) 2.5s ISI is important in displaying the sensory gating and preattentive auditory sensory memory relation.

Slow cortical potential shifts modulate P300 amplitude and topography in humans

Effects of the spontaneous slow cortical potential (SCP) shifts of the electroencephalogram (EEG) on the P300 response were investigated on ten healthy volunteers. P300 responses were recorded using an auditory oddball paradigm, where target stimuli were presented regularly after every four standard stimuli. Single event-related potential (ERP) sweeps exhibiting negative or positive SCP shifts were averaged separately. The P300 amplitude was significantly larger during negative SCP shifts. Furthermore, the topographies of P200 and P300 waves obtained during negative and positive SCP shifts showed significant differences. The results indicate that the SCP shifts in single ERP sweeps, which are considered to be correlated with the arousal or basic activity level of the cortex, explain at least part of the inter-trial variability of P300 response.

Ischemia/reperfusion in rat: Antioxidative effects of enoant on EEG, oxidative stress and inflammation

Primary objective: The present study was undertaken to evaluate whether enoant, which is rich in polyphenols, has any effect on electroencephalogram (EEG), oxidative stress and inflammation in ischemia/reperfusion (I/R) injury. Methods: Ischemia was induced by 2-hour occlusion of bilateral common carotid artery. Animals orally received enoant. Group 1 was the ischemic control group. Group 2 was treated with enoant of 1.25 g kg−1 per day for 15 days after I/R. Group 3 received the same concentration of enoant as in group 2 for 15 days before and after I/R. Group 4 was the sham operation group. EEG activities were recorded and the levels of TNF-α, IL-1β and IL-6, TBARS and GSH were measured in the whole brain homogenate. Results: There were significant changes in EEG activity in groups treated with enoant either before or after ischemia when compared with their basal EEG values. TNF-α, IL-6 and IL-1β levels were significantly increased after I/R. GSH levels in group 3 treated with enoant in both pre- and post-ischemic periods were significantly increased and TBARS concentration was decreased compared with the ischemic group. Conclusion: The findings support that both pre-ischemic and post-ischemic administrations of enoant might produce neuroprotective action against cerebral ischemia.

Movement-Related Cortical Potentials: Their Relationship to the Laterality, Complexity and Learning of a Movement

Movement-related cortical potentials (MRCPs) to self-paced unilateral movements of different laterality, complexity and practice level were recorded from 14 healthy subjects using the EMG onset as the trigger. The amplitudes at certain time points and slopes of linear regression lines fitted to 3 main shifts have been evaluated. In the early phase of MRCP the potential and slope values were symmetrically distributed around the midline maximum, which indicates that this part of MRCP can not originate from the primary motor area, which is in a contralateral relation with the movement, but from secondary motor areas (SMA and premotor areas). The changes in the voltage levels and slopes of this phase due to the changes in laterality, complexity and practice level of the movement show the relation of this activity with the abstract characteristics of the movement. The decrease of voltages and slope values in the later phases of MRCP in the complex task, which is replaced by higher voltages and slopes after a certain learning period was evaluated as a result of inhibition of associative movements via reafferent feedback signals occurring often in the first stages of learning period.

The effect of transcranial direct current stimulation on seizure frequency of patients with mesial temporal lobe epilepsy with hippocampal sclerosis

OBJECTIVES Transcranial direct current stimulation (tDCS) is a non-invasive and safe method tried in drug-resistant epilepsies, in recent years. Our aim was to evaluate the effect of tDCS in patients diagnosed with mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) which is a well-known drug-resistant focal epilepsy syndrome. PATIENTS AND METHODS Twelve MTLE-HS patients diagnosed with their typical clinical, EEG and MRI findings fulfilling the criteria for drug-resistance as suggested by the ILAE commission were included after Ethics Committee approval and their signed consent. All patients received modulated cathodal stimulation; 2mA for 30min on 3 consecutive days. All patients also received sham stimulation with the same electrode positions; designed as 60s stimulation gradually decreasing in 15s with placement of the electrodes for 30min over the stimulation side. They were followed up by standard seizure diaries and their medical treatment was not changed during the study period. Their seizure frequencies both before and after cathodal tDCS and sham stimulation were compared statistically. Adverse effects were also questioned. RESULTS Mean age of our study group was 35.42±6.96 (6 males; median: 35.50). The mean seizure frequency was 10.58±9.91 (median=8; min-max=2-30) at the baseline and significantly decreased to 1.67±2.50 (median=0.5; min-max=0-8) after cathodal tDCS application (p=0.003). Ten patients (83.33%) had more than 50% decrease in their seizure frequencies after cathodal tDCS. Two patients (16.67%) also showed positive sham effect. Six patients (50%) were seizure-free in the post-cathodal tDCS period of one month. No adverse effect has been reported except tingling sensation during cathodal stimulation. CONCLUSION Our small series suggested that cathodal tDCS may be used as an additional treatment option in MTLE-HS. It may be tried in TLE-HS patients waiting for or rejecting epilepsy surgery or even with ineffective surgery results. More studies are needed with large series of patients to investigate the effects of tDCS in drug resistant epilepsies.

Electroencephalographic characterization of scopolamine-induced convulsions in fasted mice after food intake

The present study was conducted to evaluate scopolamine-induced convulsions in fasted mice after food intake effects on the cortical electroencephalogram (EEG). Continuous EEG recordings were taken with Neuroscan for 10 min in freely moving mice with six chronic cortical electrode implants. Animals were weighed and deprived of food for 48 h. EEG recordings were taken at the 24th and 48th hour after their food deprivations. Later, all animals were treated with saline or scopolamine of 3mg/kg i.p. and EEG recordings were repeated for 10 min. Twenty minutes later, they were given food pellets and were allowed to eat ad libitum. All animals were observed for 60 min to determine the incidence and onset of convulsions and EEG recordings were taken simultaneously. The present results demonstrate that food deprivation causes differences in EEG in the elapsed time. The changes in EEG induced after food deprivation become different with scopolamine administration. In scopolamine treatment group, eating caused a series of high-voltage polyspikes and synchronized spikes with a predominant frequency in the 1-3 Hz range and fast activity that represents a typical epileptiform manifestation. It was concluded that the EEG properties and the behavioral patterns of these convulsions are in accordance with each other.