Biomedical subjects

Sidse M Arnfred

Publications and source records attributed to Sidse M Arnfred.

10 recordsLinked to original sources

PubMed2007

ERPWAVELAB a toolbox for multi-channel analysis of time-frequency transformed event related potentials.

The open source toolbox 'ERPWAVELAB' is developed for multi-channel time-frequency analysis of event related activity of EEG and MEG data. The toolbox provides tools for data analysis and visualization of the most commonly used measures of time-frequency transformed event related data as well as data decomposition through non-negative matrix and multi-way (tensor) factorization. The decompositions provided can accommodate additional dimensions like subjects, conditions or repeats and as such they are perfected for group analysis. Furthermore, the toolbox enables tracking of phase locked activity from one channel-time-frequency instance to another as well as tools for artifact rejection in the time-frequency domain. Several other features are highlighted. ERPWAVELAB can freely be downloaded from www.erpwavelab.org, requires EEGLAB [Delorme A, Makeig S. EEGLAB: an open source toolbox for analysis of single-trial EEG dynamics including independent component analysis. J Neurosci Meth 2004;134:9-21] and runs under MATLAB (The Mathworks, Inc.).

Algorithms↗

PubMed2006

Exploration of auditory P50 gating in schizophrenia by way of difference waves.

Electroencephalographic measures of information processing encompass both mid-latency evoked potentials like the pre-attentive auditory P50 potential and a host of later more cognitive components like P300 and N400.Difference waves have mostly been employed in studies of later event related potentials but here this method along with low frequency filtering is applied exploratory on auditory P50 gating data, previously analyzed in the standard format (reported in Am J Psychiatry 2003, 160:2236-8). The exploration was motivated by the observation during visual peak detection that the AEP waveform was different in the patient group, although this was not reflected by the peak measures. The sample included un-medicated schizophrenia spectrum patients (n = 17) and healthy controls (n = 24). The patients had an attenuated difference P50. This attenuation was primarily seen in the sub-sample of patients with severe negative symptoms. The difference attenuation was due to low amplitude at the first stimulus. This suggests an abnormality in readiness more than an abnormality in gating in the patient group.

Journal Article↗

PubMed2006

Delayed early proprioceptive information processing in schizophrenia.

It was first suggested that disordered proprioception was a core feature of schizophrenia by Sandor Rado in 1953. Using a recently designed proprioceptive event-related potential paradigm based on a change of load, we studied 12 unmedicated male out-patients with schizophrenia and 24 controls. In the patients, the early contralateral parietal activity was delayed and later central activity had increased amplitude, but gating was unaffected. The results could be understood within the "deficiency of corollary discharge" model of schizophrenia but not within the "filtering" theory. Further studies, including psychiatric controls, are necessary to verify the specificity of the abnormality.

Adolescent↗

PubMed2005

Parallel Factor Analysis as an exploratory tool for wavelet transformed event-related EEG.

In the decomposition of multi-channel EEG signals, principal component analysis (PCA) and independent component analysis (ICA) have widely been used. However, as both methods are based on handling two-way data, i.e. two-dimensional matrices, multi-way methods might improve the interpretation of frequency transformed multi-channel EEG of channel x frequency x time data. The multi-way decomposition method Parallel Factor (PARAFAC), also named Canonical Decomposition (CANDECOMP), was recently used to decompose the wavelet transformed ongoing EEG of channel x frequency x time (Miwakeichi, F., Martinez-Montes, E., Valdes-Sosa, P.A., Nishiyama, N., Mizuhara, H., Yamaguchi, Y., 2004. Decomposing EEG data into space-time-frequency components using parallel factor analysis. Neuroimage 22, 1035-1045). In this article, PARAFAC is used for the first time to decompose wavelet transformed event-related EEG given by the inter-trial phase coherence (ITPC) encompassing ANOVA analysis of differences between conditions and 5-way analysis of channel x frequency x time x subject x condition. A flow chart is presented on how to perform data exploration using the PARAFAC decomposition on multi-way arrays. This includes (A) channel x frequency x time 3-way arrays of F test values from a repeated measures analysis of variance (ANOVA) between two stimulus conditions; (B) subject-specific 3-way analyses; and (C) an overall 5-way analysis of channel x frequency x time x subject x condition. The PARAFAC decompositions were able to extract the expected features of a previously reported ERP paradigm: namely, a quantitative difference of coherent occipital gamma activity between conditions of a visual paradigm. Furthermore, the method revealed a qualitative difference which has not previously been reported. The PARAFAC decomposition of the 3-way array of ANOVA F test values clearly showed the difference of regions of interest across modalities, while the 5-way analysis enabled visualization of both quantitative and qualitative differences. Consequently, PARAFAC is a promising data exploratory tool in the analysis of the wavelets transformed event-related EEG.

Adult↗

PubMed2005

Acquisition of visually guided conditional associative tasks in Göttingen minipigs.

Fourteen Göttingen minipigs were trained on two different visually guided conditional associative tasks. In a spatial conditional task, a black stimulus signalled that a response to the left was correct, and a white stimulus signalled that a response to the right was correct. In a conditional go/no-go task, a blue stimulus signalled go, and a red stimulus signalled no-go. The pigs were trained until a behavioural criterion of 90% correct for each of two consecutive sessions. For the spatial conditional task, all pigs reached this criterion in 520 trials or less. For the conditional go/no-go task, all pigs, except three, reached this criterion in 1600 trials or less. Sows and boars learned equally fast. The tasks can be useful for the testing of cognitive function in pig models of human brain disorders.

Animals↗

PubMed2004

Proprioceptive event related potentials: gating and task effects.

OBJECTIVE: The integration of proprioception with vision, touch or audition is considered basic to the developmental formation of perceptions, conceptual objects and the creation of cognitive schemes. Thus, mapping of proprioceptive information processing is important in cognitive research. A stimulus of a brisk change of weight on a hand held load elicit a proprioceptive evoked potential (PEP). Here this is used to examine early and late information processing related to weight discrimination by event related potentials (ERP). METHODS: A gating paradigm having 1s between the proprioceptive stimuli of 100 g weight increase was recorded in 12 runs of 40 pairs and an 1:4 oddball task of discriminating between 40 and 100 g weight increase was both recorded in 24 healthy men. The subjects were stratified in 3 groups according to their discrimination errors. RESULTS: The proprioceptive event related potential (PERP) consisted of a contralateral parietal P60, frontal N70, midline P100, initial contralateral later widespread N160, vertex P200, parietal N290 and target related widespread P360 and posterior N500. The target related components were augmented in the best performers, while the bad performers had delayed P60 and attenuated N70. The amplitudes of N160, P200 and N290 were unrelated to performance. Gating was seen as attenuation of P100, N160 and P200 amplitude. CONCLUSIONS: The proprioceptive stimulus feature processing seem to be accomplished in the first 100 ms, while later components are modified by context as expected from previous findings in the somatosensory modality. SIGNIFICANCE: The PERP could be a useful research tool in the investigation of bodily information processing in neuropsychiatric disorders.

Adult↗

PubMed2004

Prepulse inhibition of the acoustic startle reflex in pigs and its disruption by d-amphetamine.

Prepulse inhibition (PPI) of the startle reflex is an operational measure of sensorimotor gating. The dopamine receptor agonist-mediated disruption of PPI in rats is widely used as a model of the sensorimotor gating deficiencies demonstrated in schizophrenia patients. As a possible tool for validation of a pig model of psychosis, we wished to verify the existence of PPI in landrace pigs and investigate the potential disruption of PPI by d-amphetamine (AMPH) in these animals. PPI of the acoustic startle reflex and its potential disruption by AMPH were investigated using three doses 0.5-1.5mg/kg with a paradigm including two levels of prepulses (82 and 88dB) and a prepulse (PP) interval of 60 and 120ms. We found an average PPI of the startle reflex of 25.6% and both of the investigated PP intensities and PP intervals were equally effective in this PP-inhibitive paradigm. AMPH significantly disrupted PPI and, in spite of only the 0.5mg/kg dose proved statistically significant, the results indicate this to be dose-related. We have demonstrated the phenomenon of PPI of the startle reflex in landrace pigs and its disruption by d-amphetamine. Studies of sensorimotor gating defects could be a valuable additional tool in assessing pig models of neuropsychiatric disorders.

Acoustic Stimulation↗

PubMed2004

Discriminations, reversals, and extra-dimensional shifts in the Göttingen minipig.

Göttingen minipigs were trained on a set-shifting procedure involving discriminations, reversals, and extra-dimensional shifts. The discriminations used were black-white discriminations and right-left discriminations. The initial visual and spatial discrimination seemed equally difficult, and only for the visual modality was reversal found to be more difficult than the initial discrimination. Visual reversal was more difficult than spatial reversal, and a larger number of perseverative sessions were found for visual reversal compared to spatial reversal. The acquisition of the extra-dimensional shift from the visual to the spatial dimension was not inferior to the learning of spatial reversal. Neither was the acquisition of the extra-dimensional shift from the spatial to the visual dimension inferior to the learning of visual reversal. Thus, no evidence was found for attention to stimulus dimensions in discrimination learning of the pigs.

Animals↗

PubMed2004

Exploration of somatosensory P50 gating in schizophrenia spectrum patients: reduced P50 amplitude correlates to social anhedonia.

Originally, the hypothesis of a sensory gating defect in schizophrenia evolved from studies of somatosensory evoked potentials (SEP), although the idea has primarily been pursued in the auditory modality. Gating is the relative attenuation of amplitude following the second stimulus in a stimulus pair. Recently, SEP P50 gating was seen when recording the SEP P50 in a paradigm similar to the one used for auditory P50 gating. Hypothetically, abnormality of somatosensory information processing could be related to anhedonia, which is considered a core feature of schizophrenia. Twelve unmedicated, male, schizophrenia spectrum patients (seven schizophrenic and five schizotypal personality disorder patients) and 14 age-matched healthy men participated in recordings of pair-wise presented auditory and median nerve stimuli. The patients had smaller amplitudes of the SEP P50 at the first stimulus, but no gating defect. The reduced amplitude was particularly evident in subjects with high scores on the Revised Social Anhedonia Scale. Early somatosensory information processing seems abnormal in schizophrenia spectrum patients. This could be in agreement with the theory of loss of the benefit of regularity in schizophrenia, while the results are in-conclusive regarding sensory gating theory.

Adult↗

PubMed2003

Normal p50 gating in unmedicated schizophrenia outpatients.

OBJECTIVE: The hypothesis of a sensory gating defect in schizophrenia has been supported by studies demonstrating deficient auditory P50 gating in patients. P50 gating is the relative attenuation of P50 amplitude in the auditory evoked potential following the second auditory stimulus of a stimulus pair. METHOD: Auditory evoked potentials of 12 unmedicated male patients with schizophrenia and 24 healthy men were recorded during three runs of 40 click pairs. Three alternative waveform-processing strategies were used to analyze the data. RESULTS: Regardless of strategy used, the differences between subject groups regarding P50 amplitude and gating were nonsignificant. CONCLUSIONS: The P50 gating in the patient group was normal. The results do not support the concept of the P50 gating defect as a general trait marker of schizophrenia.

Acoustic Stimulation↗