Individual differences in learning with a focus on neuropsychologic anomalies underlying learning strategies has been receiving attention in recent years. As a result, interest has increased in quantifying and analyzing cognitive behavior more directly. One of the tools that measures brain activity directly is the evoked potential (EP). This study investigated the EP recorded from the brainstem region, often referred to as brainstem auditory evoked response (BAER). The importance of BAERs in detecting pathology in the brainstem has been well documented. BAERs have also been advocated as an important tool in the electrophysiological assessment of children's brainstem function relative to learning disorders. BAER latencies were recorded, therefore, from a small group of average children and studied in relation to the BAER stability overtime. Intra-individual differences were compared to between-subject differences. So little BAER research has been performed with children that more studies are needed just to clarify normal variability of BAER parameters. The present investigation studied intra-individual differences in the stability of BAER latencies over time in young subjects with normal hearing, for comparing with and contrasting to previous results from a study using an adult sample. BAER latencies were recorded for left, right, and binaural ear presentations. A coefficient of stability (CS) was calculated for each peak, for each ear over time. ANOVA results showed significance for peak and peak by ear interaction. Several BAER parameters were examined within-subjects that may not be revealed in studies between-subjects. Profiles for intra-aural differences over time showed individual differences in the stability of the BAER. Although there appeared to be a trend toward inter-ear differences the differences did not reach significance. The profiles indicated considerable intra-aural pattern replicability, and a trend toward increase in stability over time. The results supported a need for future research on laterality studies, more age specific normative data and correlational studies in relation to individual cognitive differences.

Classical Stroop stimuli and newly developed face/word Stroop analog stimuli were used to investigate hemispheric interactions in Stroop interference effects (SEs) and corresponding event-related potentials (ERPs). Lateralized stimuli were presented unilaterally and bilaterally as congruent or incongruent color strip-word or face-word pairs (to invoke right hemisphere (RH) and left hemisphere (LH) specialization, respectively, in the latter case). The common finding for such tasks is that responses for the congruent condition are faster and more accurate than for the incongruent condition (i.e., the SE). A primary prediction is that the SE will be maximized when both the distractor and target components, or distractor alone, are presented to the specialized hemisphere (i.e., LH for words and RH for faces). A total of 88 right-handed University of North Texas students participated in one of four experiments. Participants manually responded to one component of the stimuli (i.e., color, face, or word), while ignoring the other. Behaviorally, participants showed a robust SE across all experiments, especially for the face/word task with word targets. Findings from the face/word Stroop analog tasks also indicated that SEs were produced by selective attention to either faces or words, implicating a role for top-down (controlled) processes. Hemispheric asymmetries were observed only for bilateral presentations of the face/word Stroop analog stimuli and did not differ for word versus face targets. The results suggest that the LH is less susceptible to interference from the RH than vice versa. Electrophysiologically, anterior N1 and P1, posterior P1 and N1, N2, and P3 components were identified. A SE was found for P3 amplitudes, but not latencies, across all four experiments such that the congruent condition generated greater amplitudes than the incongruent condition, suggesting that the P3 is an index of task difficulty. Surprisingly, SEs were also observed for the early ERP components, albeit embedded in higher order interactions. Taken together, the ERP evidence suggests that there is no single locus of the SE, and instead, the SE appears to be distributed over several stages of information processing.

Wavelet transform provides an alternative to the classical Short-Time Fourier Transform (STFT). In contrast to the STFT, which uses a single analysis window, the Wavelet Transform uses shorter windows at higher frequencies and longer windows at lower frequencies. For some particular wavelet functions, the local maxima of the wavelet transform correspond to the sharp variation points of the signal. As an application, wavelet transform is introduced to the character recognition. Local maximum of wavelet transform is used as a local feature to describe character boundary. The wavelet method performs well in the presence of noise. The maximum of wavelet transform is also an important feature for analyzing the properties of brain wave. In our study, we found the maximum of wavelet transform was related to the P300 latency. It provides an easy and efficient way to measure P300 latency.

Event related potentials (ERP's) carry very important information that relates to the performance of the brain functions of the human being. Further studies have identified that one component, in particular, P 300, is affected by the memory process. Matched filter is used to improved the SNR of signal ERP' s. We use the output of the matched filter to distinguish the difference of the waveforms between normal subjects and memory-impaired subjects. In our study, we found that the peak values of the matched filtering output were different between normal subjects and memoryimpaired subjects. Also, as an application, wavelet transform is introduced to the ERP analysis. Local maximum of wavelet transform was used as a local feature to find the relationship between the sharp variation points and the memory process. A comparison between matched filtering and wavelet transform was made and also the correlation coefficients of the peaks and sharp variation points are calculated to find the relationship between the important moments in a memory process.

Attention-deficit/hyperactivity disorder (ADHD) is a common childhood psychiatric disorder characterized by developmentally inappropriate levels of inattentiveness, impulsivity and hyperactivity. Current theories of ADHD cite evidence from neuropsychological and brain imaging studies suggesting that abnormalities in the structure and function of the frontal lobes and connected brain regions are associated with impaired behavioural inhibition, constituting the primary deficit in ADHD. While most reviewers conclude that neuropsychological studies have failed to find specific deficits in various aspects of attention in ADHD, poor performance on attentional tasks, including the continuous performance task (CPT), is a common finding and previous electrophysiological studies suggest evidence of impaired attentional processing. This study aimed to investigate the cortical activity associated with attentional processes in children with and without ADHD, using steady-state probe topography (SSPT). Seventeen boys diagnosed with ADHD and seventeen age matched control boys participated. Changes in the amplitude and latency of the steady-state visually evoked potential (SSVEP) associated with correct responses to targets in the �X� and �AX� versions of the CPT were examined. At critical time points in both tasks, the control group demonstrated SSVEP changes suggesting increased activation and increased speed of neural processing. These effects occurred predominantly in medial frontal, right prefrontal, right parietal and occipital regions, suggesting enhanced activity in regions previously shown to be involved in attentional processes. The ADHD group demonstrated much smaller increases in activation and processing speed in frontal regions and predominantly reduced activation and slower processing in parieto-occipital regions. Group differences suggesting reduced activity in the ADHD group were observed in response to the presentation of both cues and targets, as well as in the intervals leading up to target presentation, especially in the cued CPT-AX. These results suggest that processing of task relevant stimuli as well as preparatory and motor processes may be associated with dysfunctional activation of brain networks of attention in ADHD, involving deficits in both frontal and parietal cortical regions. These regions may also be involved in the maintenance of information required for correct task performance and the results also suggest possible deficits in these processes in ADHD. The findings are consistent with others of reduced activation and cognitive deficits in ADHD involving these brain regions and networks, and with the idea that ADHD may be associated with a diminished ability to regulate levels of arousal and activation appropriate to task demands.

Bibliography: leaves 156-173 / x, 173 leaves, [6] leaves of plates : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (D.M.)--University of Adelaide, 1986

University of Macau / Faculty of Science and Technology / Department of Electrical and Electronics Engineering

Previous evidence has shown that older adults may have specific declines in prefrontal cortex (PFC)-mediated processes supported source memory retrieval, such as strategic retrieval and post-retrieval monitoring. This decline may manifest in the form of attenuated late-frontal ERP effects. Behavioral research suggests that explicitly integrating a target context, or source, with a stimulus during encoding will improve subsequent source memory performance for both younger and older adults. Explicit item-feature binding instructions during encoding may alleviate source memory impairments, in part, by reducing the need for strategic processing during episodic retrieval. The present ERP study investigated whether explicit direction of attention toward item-feature integration may reduce age-related deficits in source memory by alleviating the necessity of frontally-mediated strategic processing at retrieval. Results demonstrated that explicit direction of attention improved source memory accuracy for both young and older adults, but older adults benefited less than the young, indicating additional age-related deficits. ERPs revealed that explicit encoding support attenuated post-retrieval monitoring effects in the young. In the old, explicit encoding instruction resulted in earlier onset of early frontal effects, possibly related to familiarity. Results suggest explicit direction of attention toward item-source integration at encoding may improve source memory by alleviating the need for strategic retrieval, but age-related deficits persist.

Thesis (M. Sc.)--University of Canterbury, 2009. / Typescript (photocopy). Includes bibliographical references (leaves 82-94). Also available via the World Wide Web.

Thesis (doctoral)--Universität Leipzig, 2001. / Includes bibliographical references (p. 141-159).