Medial Temporal Lobe Atrophy in Older Adults With Subjective Cognitive Impairments Affects Gait Parameters in the Spatial Navigation Task.

Both navigation abilities and gait can be affected by the atrophy in the medial temporal cortex. This study aimed to determine whether navigation abilities could differentiate seniors with and without medial temporal lobe atrophy who complained about their cognitive status. The participants, classified to either the medial temporal atrophy group (n = 23) or the control group (n = 22) underwent neuropsychological assessment and performed a spatial navigation task while their gait parameters were recorded. The study showed no significant differences between the two groups in memory, fluency, and semantic knowledge or typical measures of navigating abilities. However, gait parameters, particularly the propulsion index during certain phases of the navigation task, distinguished between seniors with and without medial temporal lobe lesions. These findings suggest that the gait parameters in the navigation task may be a valuable tool for identifying seniors with cognitive complaints and subtle medial temporal atrophy.

Visual attention does not affect the reliability of otoacoustic emission or medial olivocochlear reflex.

This study investigated whether visual attention affects the reliability (i.e., repeatability) of transiently evoked otoacoustic emission (TEOAE) magnitudes or of medial olivocochlear reflex (MOCR) estimates. TEOAEs were measured during three visual attentional conditions: control (subject were seated with eyes closed); passive (subjects looked at a pattern of squares on a computer screen); and active (subjects silently counted an occasionally inverted pattern). To estimate reliability, the whole recording session was repeated the next day. The results showed that visual attention does not significantly affect TEOAE or MOCR magnitudes-or their reliability. It is therefore possible to employ visual stimuli (e.g., watching a silent movie) during TEOAE experiments, a procedure sometimes used during testing to prevent subjects from falling asleep or to keep children still and quiet.

Easy and Hard Auditory Tasks Distinguished by Otoacoustic Emissions and Event-related Potentials: Insights into Efferent System Activity.

The medial olivocochlear (MOC) system is thought to be responsible for modulation of peripheral hearing through descending (efferent) pathways. This study investigates the connection between peripheral hearing function and auditory attention tasks of different degrees of difficulty. Peripheral hearing function was evaluated by analyzing the amount of change in otoacoustic emissions (OAEs) by contralateral acoustic stimulation (CAS), a well-known effect of the MOC system. Simultaneously, levels of attention were evaluated by event-related potentials (ERPs). The ERPs showed clear differences in processing tasks of different difficulty, but paradoxically there was no difference in the amount of OAE change brought about by CAS. There was also no effect on OAE latency, nor was there any difference in noise level or number of rejected trials. However, we observed that the changes in OAEs by CAS for easy and hard tasks were correlated with the magnitude of the P3 wave in the ERP. This suggests there might be some sort of mutual compensation mechanism - presently unknown - between periphery and cortex.

No Change in Medial Olivocochlear Efferent Activity during an Auditory or Visual Task: Dual Evidence from Otoacoustic Emissions and Event-Related Potentials.

The medial olivocochlear (MOC) system is thought to be responsible for modulation of peripheral hearing through descending (efferent) pathways. This study investigated the connection between peripheral hearing function and conscious attention during two different modality tasks, auditory and visual. Peripheral hearing function was evaluated by analyzing the amount of suppression of otoacoustic emissions (OAEs) by contralateral acoustic stimulation (CAS), a well-known effect of the MOC. Simultaneously, attention was evaluated by event-related potentials (ERPs). Although the ERPs showed clear differences in processing of auditory and visual tasks, there were no differences in the levels of OAE suppression. We also analyzed OAEs for the highest magnitude resonant mode signal detected by the matching pursuit method, but again did not find a significant effect of task, and no difference in noise level or number of rejected trials. However, for auditory tasks, the amplitude of the P3 cognitive wave negatively correlated with the level of OAE suppression. We conclude that there seems to be no change in MOC function when performing different modality tasks, although the cortex still remains able to modulate some aspects of MOC activity.

Electrophysiological correlates of focused attention on low- and high-distressed tinnitus.

OBJECTIVES: The study aimed at determining the EEG correlates of concentration on either low or high-distressed tinnitus. METHODS: Sixty-seven patients (36 women, mean age = 50.34 ± 12.94 years) with chronic tinnitus were assigned to either a high (HD) or low (LD) tinnitus-related distress group based on THI results. All participants took part in the EEG study comprising two 3-4 min blocks of focusing on either tinnitus (Tinnitus Focus Condition, TFC) or the sensations from one's own body (Body Focus Condition, BFC). The absolute power and current density of 8 frequency bands in 7 clusters were compared between conditions and groups. RESULTS: The most pronounced differences were found in the HD patients in the TFC, relative to the BFC, i.e. reduced power of frontally distributed low alpha (8-10 Hz) and posterior high alpha (10-12 Hz) as well as lower current density of 8-10 Hz rhythm over the right frontal/anterior cingulate cortex and higher middle beta (15-18 Hz) density in the precuneus. The HD, relative to LD patients, in both conditions, exhibited increased low beta (12-15 Hz) power over the left middle area and greater higher beta (15-25 Hz) power in the left posterior region. CONCLUSIONS: The present study contrasted bioelectrical activity, acquired when concentrating on tinnitus with EEG data collected whilst patients focused on their body. Decreased alpha power and current density in the frontal/cingulate cortex when listening to bothersome tinnitus might reflect greater cortical arousal whereas increased beta power and density in the precuneus/posterior cingulate activity in this condition could be indicative for elevated tension or augmented cognitive/emotional processing of tinnitus sound. Enhanced beta rhythm in patients with high versus low tinnitus distress, observed independently of the study condition, may be due to greater self-focused attention or more active processing of sensations derived from the own body.

Early general development and central auditory system maturation in children with cochlear implants - A case series.

OBJECTIVES: A cochlear implant (CI) has the potential to improve the functioning of a deaf child in many aspects. Nevertheless, the dynamics of the general development, beyond the typically measured language abilities, directly after CI, is still unknown, especially if a child is implanted early. In this study we present a methodological framework for assessment of different domains of development, as well as the central auditory nervous system (CANS) maturation in infants and toddlers with a CI. METHODS: Three children with bilateral congenital hearing loss and a unilateral CI, aged below 2.5 years, participated in a longitudinal study. Children were tested at three time points after cochlear implantation using the Polish Children Development Scale (CDS) consisting of a comprehensive battery of tests, as well as recordings of Cortical Auditory Evoked Potentials (CAEP). RESULTS: All three children revealed gradual improvement in the overall CDS result as well as most of the CDS subscales. After 9 months of CI experience two younger children showed age-appropriate performance. In CAEP measurements a decrease of latency of the P1 component (an established biomarker of cortical auditory maturation) was observed in the same two children, with one achieving normal ranges of P1 latency after 9 months of CI use. CONCLUSIONS: Our novel methodological framework can be successfully applied in small children with cochlear implants. It contributes to better understanding of the general development in early implanted children. The preliminary results indicate variability in children's performance in various developmental domains and thus the need to monitor the development of each child individually and holistically.

Abnormal Resting-State Quantitative Electroencephalogram in Children With Central Auditory Processing Disorder: A Pilot Study.

In this study, we showed an abnormal resting-state quantitative electroencephalogram (QEEG) pattern in children with central auditory processing disorder (CAPD). Twenty-seven children (16 male, 11 female; mean age = 10.7 years) with CAPD and no symptoms of other developmental disorders, as well as 23 age- and sex-matched, typically developing children (TDC, 11 male, 13 female; mean age = 11.8 years) underwent examination of central auditory processes (CAPs) and QEEG evaluation consisting of two randomly presented blocks of "Eyes Open" (EO) or "Eyes Closed" (EC) recordings. Significant correlations between individual frequency band powers and CAP tests performance were found. The QEEG studies revealed that in CAPD relative to TDC there was no effect of decreased delta absolute power (1.5-4 Hz) in EO compared to the EC condition. Furthermore, children with CAPD showed increased theta power (4-8 Hz) in the frontal area, a tendency toward elevated theta power in EO block, and reduced low-frequency beta power (12-15 Hz) in the bilateral occipital and the left temporo-occipital regions for both EO and EC conditions. Decreased middle-frequency beta power (15-18 Hz) in children with CAPD was observed only in the EC block. The findings of the present study suggest that QEEG could be an adequate tool to discriminate children with CAPD from normally developing children. Correlation analysis shows relationship between the individual EEG resting frequency bands and the CAPs. Increased power of slow waves and decreased power of fast rhythms could indicate abnormal functioning (hypoarousal of the cortex and/or an immaturity) of brain areas not specialized in auditory information processing.

Heightened visual attention does not affect inner ear function as measured by otoacoustic emissions.

Previous research has indicated that inner ear function might be modulated by visual attention, although the results have not been totally conclusive. Conceivably, modulation of hearing might occur due to stimulation of the cochlea via descending medial olivocochlear (MOC) neurons. The aim of the present study was to test whether increased visual attention caused corresponding changes in inner ear function, which was measured by the strength of otoacoustic emissions (OAEs) recorded from the ear canal in response to a steady train of clicks. To manipulate attention, we asked subjects to attend to, or ignore, visual stimuli delivered according to an odd-ball paradigm. The subjects were presented with two types of visual stimuli: standard and deviant (20% of all stimuli, randomly presented). During a passive part of the experiment, subjects had to just observe a pattern of squares on a computer screen. In an active condition, the subject's task was to silently count the occasional inverted (deviant) pattern on the screen. At all times, visual evoked potentials (VEPs) were used to objectively gauge the subject's state of attention, and OAEs in response to clicks (transiently evoked OAEs, TEOAEs) were used to gauge inner ear function. As a test of descending neural activity, TEOAE levels were evaluated with and without contralateral acoustic stimulation (CAS) by broadband noise, a paradigm known to activate the MOC pathway. Our results showed that the recorded VEPs were, as expected, a good measure of visual attention, but even when attention levels changed there was no corresponding change in TEOAE levels. We conclude that visual attention does not significantly affect inner ear function.

Slow Cortical Potential Neurofeedback in Chronic Tinnitus Therapy: A Case Report.

This study is the first to demonstrate outcomes of slow cortical potential (SCP) Neurofeedback training in chronic tinnitus. A 50-year old male patient with tinnitus participated in three SCP training blocks, separated with 1-month breaks. After the training the patient reported decreased tinnitus loudness and pitch, as well as improved quality of daily life. A quantitative electroencephalography analysis revealed close to normal changes of resting state bioelectrical activity in cortical areas considered to be involved in tinnitus generation. The present case study indicates that SCP Neurofeedback training can be considered a promising method for tinnitus treatment.

[The possibilities and limitations of simultaneous EEG-fMRI registration--the alpha rhythm study]. / Mozliwosci i problemy jednoczesnych rejestracji EEG-fMRI--badanie rytmu alfa.

INTRODUCTION: Simultaneous EEG-fMRI registration is rapidly evolving and has received substantial attention. This technique provides precise information in both spatial and temporal domain. The biological basis of the EEG and fMRI signal is different which, on the one hand makes results interpretation more difficult but, on the other hand, gives more convincing arguments on the neural correlates of sensory and cognitive processes. In this paper we present an example of implementation of simultaneous EEG-fMRI registration for alpha rhythm source mapping. MATERIAL AND METHODS: 60 young males took part in this study. For the group analysis we selected 33 individuals to obtain homogenous group. Siemens Magnetom Trio 3T and 64-electrode SynAmp2 Neuroscan EEG system was applied. Participants took part in fMRI imaging which adapted arrest reaction study. RESULTS: Averaged spectra amplitude distribution of alpha rhythm (8-13Hz) showed high activation in the occipito-parietal region and smaller but noticeable activity in the frontal area. FMRI results revealed activity in bilateral occipital lobe. Additional regions included the posterior cingulate gyrus, middle and superior frontal gyrus. Statistically significant areas with BOLD signal decrease were located in the temporal lobe and anterior cingulate gyrus. CONCLUSION: The obtained results indicate overlapping regions of the presented EEG outcomes and fMRI maps for alpha rhythm study. Simultaneous EEG-fMRI technique allows for registration of spontaneous EEG activity with both high temporal and spatial resolution. The alpha rhythm might reflect the extensive brain process involving the thalamo-occipito-frontal connections.

Attention dysfunction subtypes of developmental dyslexia.

BACKGROUND: Previous studies indicate that many different aspects of attention are impaired in children diagnosed with developmental dyslexia (DD). The objective of the present study was to identify cognitive profiles of DD on the basis of attentional test performance. MATERIAL/METHODS: 78 children with DD (30 girls, 48 boys, mean age of 12 years ±8 months) and 32 age- and sex-matched non-dyslexic children (14 girls, 18 boys) were examined using a battery of standardized tests of reading, phonological and attentional processes (alertness, covert shift of attention, divided attention, inhibition, flexibility, vigilance, and visual search). Cluster analysis was used to identify subtypes of DD. RESULTS: Dyslexic children showed deficits in alertness, covert shift of attention, divided attention, flexibility, and visual search. Three different subtypes of DD were identified, each characterized by poorer performance on the reading, phonological awareness, and visual search tasks. Additionally, children in cluster no. 1 displayed deficits in flexibility and divided attention. In contrast to non-dyslexic children, cluster no. 2 performed poorer in tasks involving alertness, covert shift of attention, divided attention, and vigilance. Cluster no. 3 showed impaired covert shift of attention. CONCLUSIONS: These results indicate different patterns of attentional impairments in dyslexic children. Remediation programs should address the individual child's deficit profile.

Towards neural correlates of auditory stimulus processing: a simultaneous auditory evoked potentials and functional magnetic resonance study using an odd-ball paradigm.

BACKGROUND: The neural underpinnings of auditory information processing have often been investigated using the odd-ball paradigm, in which infrequent sounds (deviants) are presented within a regular train of frequent stimuli (standards). Traditionally, this paradigm has been applied using either high temporal resolution (EEG) or high spatial resolution (fMRI, PET). However, used separately, these techniques cannot provide information on both the location and time course of particular neural processes. The goal of this study was to investigate the neural correlates of auditory processes with a fine spatio-temporal resolution. A simultaneous auditory evoked potentials (AEP) and functional magnetic resonance imaging (fMRI) technique (AEP-fMRI), together with an odd-ball paradigm, were used. MATERIAL AND METHODS: Six healthy volunteers, aged 20-35 years, participated in an odd-ball simultaneous AEP-fMRI experiment. AEP in response to acoustic stimuli were used to model bioelectric intracerebral generators, and electrophysiological results were integrated with fMRI data. RESULTS: fMRI activation evoked by standard stimuli was found to occur mainly in the primary auditory cortex. Activity in these regions overlapped with intracerebral bioelectric sources (dipoles) of the N1 component. Dipoles of the N1/P2 complex in response to standard stimuli were also found in the auditory pathway between the thalamus and the auditory cortex. Deviant stimuli induced fMRI activity in the anterior cingulate gyrus, insula, and parietal lobes. CONCLUSIONS: The present study showed that neural processes evoked by standard stimuli occur predominantly in subcortical and cortical structures of the auditory pathway. Deviants activate areas non-specific for auditory information processing.

A modified oddball paradigm for investigation of neural correlates of attention: a simultaneous ERP-fMRI study.

INTRODUCTION: The objective of the presented study was to develop and evaluate a P300 experimental protocol for simultaneous registration of event-related potentials (ERPs) and functional MRI (fMRI) data with continuous imaging. It may be useful for investigating attention and working memory processes in specific populations, such as children and neuropsychiatric patients. MATERIALS AND METHODS: Eleven children were investigated with simultaneous ERP-fMRI. To fulfill requirements of both BOLD and electroencephalographic signal registration, a modified oddball task was used. To verify the ERP-fMRI protocol we also performed a study outside the scanner using a typical two-stimuli oddball paradigm. RESULTS: Localization of the P300 component of ERPs partially corresponded with fMRI results in the frontal and parietal brain regions. FMRI activations were found in: middle frontal gyrus, insula, SMA, parietal lobule, thalamus, and cerebellum. Our modified oddball task provided ERP-fMRI results with high level of significance (EEG SNR=35, fMRI p<0.05-Bonf.). ERPs obtained in the scanner were comparable with those registered outside the scanner, although some differences in the amplitude were noticed, mainly in the N100 component. CONCLUSION: In our opinion the presented paradigm may be successfully applied for simultaneous ERP-fMRI registration of neural correlates of attention in vulnerable populations.

[Application of simultaneous auditory evoked potentials and functional magnetic resonance recordings for examination of central auditory system--preliminary results]. / Wykorzystanie jednoczesnych rejestracji sluchowych potencjalów korowych i funkcjonalnego rezonansu magnetycznego do badania procesów osrodkowej czesci ukladu sluchowego--wyniki wstepne.

INTRODUCTION: Processing of auditory information in central nervous system bases on the series of quickly occurring neural processes that cannot be separately monitored using only the fMRI registration. Simultaneous recording of the auditory evoked potentials, characterized by good temporal resolution, and the functional magnetic resonance imaging with excellent spatial resolution allows studying higher auditory functions with precision both in time and space. THE AIM OF THE STUDY: was to implement the simultaneous AEP-fMRI recordings method for the investigation of information processing at different levels of central auditory system. MATERIAL AND METHODS: Five healthy volunteers, aged 22-35 years, participated in the experiment. The study was performed using high-field (3T) MR scanner from Siemens and 64-channel electrophysiological system Neuroscan from Compumedics. Auditory evoked potentials generated by acoustic stimuli (standard and deviant tones) were registered using modified odd-ball procedure. Functional magnetic resonance recordings were performed using sparse acquisition paradigm. The results of electrophysiological registrations have been worked out by determining voltage distributions of AEP on skull and modeling their bioelectrical intracerebral generators (dipoles). FMRI activations were determined on the basis of deviant to standard and standard to deviant functional contrasts. Results obtained from electrophysiological studies have been integrated with functional outcomes. RESULTS: Morphology, amplitude, latency and voltage distribution of auditory evoked potentials (P1, N1, P2) to standard stimuli presented during simultaneous AEP-fMRI registrations were very similar to the responses obtained outside scanner room. Significant fMRI activations to standard stimuli were found mainly in the auditory cortex. Activations in these regions corresponded with N1 wave dipoles modeled based on auditory potentials generated by standard tones. Auditory evoked potentials to deviant stimuli were recorded only outside the MRI scanner. However, deviant stimuli induced significant fMRI activations. They were observed mainly in the anterior cingulate gyrus, insula and parietal lobes. These regions of the brain are related to attention and decision-making processes. CONCLUSIONS: The results showed that applied paradigm is suitable for investigation of acoustic processing on the level of auditory cortex. Technique of the simultaneous AEP-fMRI registrations seems to be promising for investigation of more complex nervous processes in central auditory system with good temporo-spatial resolution.

Cortical responsiveness is reduced during P300 potential. Does the level of initial activity affect this inhibition?

The regulation of firing thresholds of cortical pyramidal cells has been suggested as one of the mechanisms underlying the generation of the P300 component of the human event-related potential. According to this hypothesis, the detection of an important stimulus produces a widespread inhibition of "irrelevant" networks, interrupting the ongoing cortical activity and facilitating the analysis of the important information. In the present experiment, target stimuli in a standard "odd-ball" paradigm were used as important events. The cortical responsiveness was measured using the responses to additional probing stimuli delivered 400 ms and 1,000 ms after target and non-target stimuli. The subjects were asked to count mentally the target stimuli and ignore the non-targets and the probes. The level of "irrelevant" cortical activity was manipulated using additional visual noise stimulation. Event-related potentials were recorded at Fz, Cz, Pz and Oz scalp sites. Our results showed that the noise reduced the initial responses to target and non-target stimuli in Oz, Pz and Cz but not in Fz recordings. The noise reduced the probe responses in Oz and Pz but not in Cz and Fz recordings. The amplitudes of P300 components were not affected by the noise. The target stimuli reduced the subsequent probe responses in Pz and Cz but not in Oz and Fz recordings. Thus, the effects of noise and target detection were not identical in the different regions of cortex. The other important outcome of our study was that the target stimuli suppressed the effects of noise. The effect of noise on probe responses was significant in the non-target but not in the target trials. The effect of noise was significant if the probes were delivered 1,000 ms after "odd-ball" stimuli, but it was insignificant when the delay was only 400 ms. Such results support the hypothesis that important information reduces cortical responses to other, irrelevant stimuli.