Development and evaluation of a smartphone-based electroencephalography (EEG) system

The aim of the study was to design, develop and evaluate a general-purpose EEG platform which integrates with a smartphone. The target specification was a system with 19 EEG channels and data stored onto the smartphone via a Wi-Fi connection. The hardware was developed using three ADS1299 integrated circuits, and the game engine, Unity, was used to develop the smartphone app. An evaluation of the system was conducted using recordings of alpha waves during periods of eye closure in participants (Bland-Altman statistical comparison with a clinical grade EEG system). The smartphone was also used to deliver time-locked auditory stimuli using an oddball paradigm to evaluate the ability of the developed system to acquire event related potentials (ERP) during sitting and walking. No significant differences were found for the alpha wave peak amplitude, frequency and area under the curve for the intra-system (two consecutive periods of alpha waves) or inter-system (developed smartphone-based EEG system versus FDA-approved system) comparisons. ERP results showed the peak amplitude of the auditory P300 component to deviant tones was significantly higher when compared to standard tones for sitting and walking activities. It is envisaged that our general-purpose EEG system will encourage other researchers to design and build their own specific versions rather than being limited by the fixed features of commercial products

A comparative experimental study of visual brain event-related potentials to a working memory task: virtual reality head-mounted display versus a desktop computer screen

Virtual reality head mounted display (VR HMD) systems are increasingly utilised in combination with electroencephalography (EEG) in the experimental study of cognitive tasks. The aim of our investigation was to determine the similarities/differences between VR HMD and the computer screen (CS) in response to an n-back working memory task by comparing visual electrophysiological event-related potential (ERP) waveforms (N1/P1/P3 components). The same protocol was undertaken for VR HMD and CS with participants wearing the same EEG headcap. ERP waveforms obtained with the VR HMD environment followed a similar time course to those acquired in CS. The P3 mean and peak amplitudes obtained in VR HMD were not significantly different to those obtained in CS. In contrast, the N1 component was significantly higher in mean and peak amplitudes for the VR HMD environment compared to CS at the frontal electrodes. Significantly higher P1 mean and peak amplitudes were found at the occipital region compared to the temporal for VR HMD. Our results show that successful acquisition of ERP components to a working memory task is achievable by combining VR HMD with EEG. In addition, the higher amplitude N1/P1 components seen in VR HMD indicates the potential utility of this VR modality in the investigation of early ERPs. In conclusion, the combination of VR HMD with EEG/ERP would be a useful approach to advance the study of cognitive function in experimental brain research

Response of face-selective brain regions to trustworthiness and gender of faces

Neuropsychological and neuroimaging studies have demonstrated a role for the amygdala in processing the perceived trustworthiness of faces, but it remains uncertain whether its responses are linear (with the greatest response to the least trustworthy-looking faces), or quadratic (with increased fMRI signal for the dimension extremes). It is also unclear whether the trustworthiness of the stimuli is crucial or if the same response pattern can be found for faces varying along other dimensions. In addition, the responses to perceived trustworthiness of face-selective regions other than the amygdala are seldom reported. The present study addressed these issues using a novel set of stimuli created through computer image-manipulation both to maximise the presence of naturally occurring cues that underpin trustworthiness judgments and to allow systematic manipulation of these cues. With a block-design fMRI paradigm, we investigated neural responses to computer-manipulated trustworthiness in the amygdala and core face-selective regions in the occipital and temporal lobes. We asked whether the activation pattern is specific for differences in trustworthiness or whether it would also track variation along an orthogonal male–female gender dimension. The main findings were quadratic responses to changes in both trustworthiness and gender in all regions. These results are consistent with the idea that face-responsive brain regions are sensitive to face distinctiveness as well as the social meaning of the face features

Acupuncture needling sensation: the neural correlates of deqi using fMRI

The needling sensation of deqi is considered by most acupuncturists to be an important component of acupuncture, yet neuroimaging research that investigates this needle sensation has been limited. In this study we have investigated the effect of deqi and acute pain needling sensations upon brain fMRI blood oxygen level-dependent (BOLD) signals. Seventeen right-handed participants who received acupuncture at the right LI-4 (Hegu) acupoint were imaged in a 3T MRI scanner. fMRI datasets were classified, on the basis of psychophysical participants' reports of needling scores, into those that were associated with predominantly deqi sensations versus those with predominantly acute pain sensations. Brain areas showing changes in BOLD signal increases (activations) and decreases (deactivations) were identified. Differences were demonstrated in the pattern of activations and deactivations between groupings of scans associated with deqi versus pain sensations. For the deqi grouping, significant deactivations occurred, whereas significant activations did not. In contrast, the predominantly acute pain grouping was associated with a mixture of activations and deactivations. For the comparison between the predominately deqi sensation grouping and the acute pain sensation grouping (deqi>pain contrast), only negative Z value voxels resulted (mainly from deactivations in the deqi grouping and activations in the pain grouping) in the limbic/sub-cortical structures and the cerebellum regions of interest. Our results show the importance of collecting and accounting for needle sensation data in neuroimaging studies of acupunctur

An amygdala response to fearful faces with covered eyes

Findings of amygdala responsiveness to the eye region of fearful faces raise the question of whether eye widening is the only facial cue involved. We used fMRI to investigate the differential amygdala response to fearful versus neutral stimuli for faces, eyes, and for faces in which the eye region was masked. For maximum sensitivity, a block design was used, with a region of interest (ROI) centred on the amygdala which included peri-amygdalar areas. Evidence of amygdala responsiveness to fear compared to neutral stimuli was found for whole faces, eye region only, and for faces with masked eyes. The amygdala can therefore use information from facial regions other than the eyes, allowing it to respond differentially to fearful compared to neutral faces even when the eye region is hidde

Brain imaging of acupuncture: comparing superficial with deep needling

The difference between superficial and deep needling at acupuncture points has yet to be mapped with functional magnetic resonance imaging (fMRI). Using a 3 T MRI, echo planar imaging data were acquired for 17 right-handed healthy volunteer participants. Two fMRI scans of acupuncture needling were taken in random order in a block design, one for superficial and one for deep needling on the right hand at the acupuncture point LI-4 (Hegu), with the participant blind to the order. For both scans needle stimulation was used. Brain image analysis tools were used to explore within-group and between-group differences in the blood oxygen level dependent (BOLD) responses. The study demonstrated marked similarities in BOLD signal responses between superficial and deep needling, with no significant differences in either activations (increases in BOLD signal) or deactivations (decreases in BOLD signal) above the voxel Z score of 2.3 with corrected cluster significance of P = 0.05. For both types of needling, deactivations predominatid over activations. These fMRI data suggest that acupuncture needle stimulation at two different depths of needling, superficial and deep, do not elicit significantly different BOLD responses. This data is consistent with the equivalent therapeutic outcomes that are claimed by proponents of Japanese and Chinese styles of acupuncture that utilise superficial and deep needling, respectively