A key question in the investigation of awareness is whether it can occur without attention, or vice versa. Most evidence to date suggests that attention is necessary for awareness of visual stimuli, but that attention can sometimes be present without corresponding aware-ness. However, there has been some evidence that natural scenes in general, and in particular scenes including animals, may not require visual attention for a participant to become aware of their gist. One relatively recent paradigm for providing evidence for animal awareness without attention (Li, VanRullen, Koch, & Perona, 2002) requires participants to perform an attention demanding primary task while also determining whether a photograph displayed briefly in the periphery contains an animal as a secondary task. However, Cohen, Alvarez, and Nakayama (2011) questioned whether the primary task in these experiments used up all the available attentional capacity. Their experiments used a more demanding primary task to be sure attention really was not available for the image-recognition task, and the results indicated that attention was contributing to the animal detection task. However, in addition to changing the primary task, they displayed the stimuli for the two tasks superimposed on each other in the same area of the visual field. The experiment reported here is similar to the one by Cohen et al., but with the stimuli for the two tasks separated spatially. Animal recognition with separated stimuli was impaired by additionally performing the attention-demanding task, leaving no good evidence that it is possible to recognize natural scenes without attention, in turn removing this support for awareness without attention.

Text in Afrikaans / Hierdie studie ondersoek die moontlikheid dat aandagtekort versteuring met hiperaktiwiteit(ATHV/H) verband hou met probleme met voortgesette aandag, terwyl aandagtekort versteuring sander hiperaktiwiteit(ATHV/SO) verband hou met probleme met gefokusde aandag. Neurosielkundige toetse waarmee voortgesette- en gefokusde aandag gemeet word, word gebruik om drie groepe, naamlik ATHV/H(n=24), ATHV/SO(n=l5) en 'n kontrole groep(n=21), met mekaar te vergelyk. Resul tate dui daarop dat die groep ATHV/SO beduidend swakker presteer as die ander twee groepe op sommige van die toetse van gefokusde aandag, en ook neig om swakker te presteer op die toets van voortgesette aandag. Die groep ATHV/SO se probleme blyk gekoppel te wees aan 'n stadiger spoed van kognitiewe prosessering en 'n toestand van hipoopwekking. Die groep ATHV/H presteer nie beduidend swakker as die ander twee groepe op die toets van voortgesette aandag nie, maar presteer wel swakker as die kontrole groep op die Stroop Colour-Word Test waar inhibisie van ontoepaslike response vereis word. Die groep ATHV /H se probleme blyk verband te hou met frontale disfunksie wat manifesteer as 'n neighing tot impulsiwiteit en gebrekkige gedragsregulering. / This study examined the possibility that attention deficit disorder with hyperactivity(ADHD/H) is related to problems with sustained attention, while attention deficit disorder without hyperactivity (ADHD/WO) is related to problems with focussed attention. The performance of three groups: ADHD/H (n=24), ADHD/WO(n=15) and a control group(n=21) were compared. Results indicated that the ADHD/WO group performed significantly poorer than the other two groups on some of the tests of focussed attention and also tended to perform poorer on the test assessing sustained attention. This groups' symtoms appear to be related to a slowed speed of processing and a state of hypo-arousal. The ADHD/H group did not perform poorer than the other two groups on the test assessing sustained attention. The ADHD/H groups' symptoms appear to be related to frontal dysfunction resulting in impulsivity and poor behavioural control. / Psychology / M.A. (Sielkunde)

Text in Afrikaans / Hierdie studie ondersoek die moontlikheid dat aandagtekort versteuring met hiperaktiwiteit(ATHV/H) verband hou met probleme met voortgesette aandag, terwyl aandagtekort versteuring sander hiperaktiwiteit(ATHV/SO) verband hou met probleme met gefokusde aandag. Neurosielkundige toetse waarmee voortgesette- en gefokusde aandag gemeet word, word gebruik om drie groepe, naamlik ATHV/H(n=24), ATHV/SO(n=l5) en 'n kontrole groep(n=21), met mekaar te vergelyk. Resul tate dui daarop dat die groep ATHV/SO beduidend swakker presteer as die ander twee groepe op sommige van die toetse van gefokusde aandag, en ook neig om swakker te presteer op die toets van voortgesette aandag. Die groep ATHV/SO se probleme blyk gekoppel te wees aan 'n stadiger spoed van kognitiewe prosessering en 'n toestand van hipoopwekking. Die groep ATHV/H presteer nie beduidend swakker as die ander twee groepe op die toets van voortgesette aandag nie, maar presteer wel swakker as die kontrole groep op die Stroop Colour-Word Test waar inhibisie van ontoepaslike response vereis word. Die groep ATHV /H se probleme blyk verband te hou met frontale disfunksie wat manifesteer as 'n neighing tot impulsiwiteit en gebrekkige gedragsregulering. / This study examined the possibility that attention deficit disorder with hyperactivity(ADHD/H) is related to problems with sustained attention, while attention deficit disorder without hyperactivity (ADHD/WO) is related to problems with focussed attention. The performance of three groups: ADHD/H (n=24), ADHD/WO(n=15) and a control group(n=21) were compared. Results indicated that the ADHD/WO group performed significantly poorer than the other two groups on some of the tests of focussed attention and also tended to perform poorer on the test assessing sustained attention. This groups' symtoms appear to be related to a slowed speed of processing and a state of hypo-arousal. The ADHD/H group did not perform poorer than the other two groups on the test assessing sustained attention. The ADHD/H groups' symptoms appear to be related to frontal dysfunction resulting in impulsivity and poor behavioural control. / Psychology / M.A. (Sielkunde)

Indications are that autonomic under-arousal exists in children with ADHD. Published results are, however, controversial and few studies examine the relationship between the autonomic nervous system and focussed attention. In line with the indications of sympathetic under-arousal, patients with the disorder are treated with sympathomimetic stimulants such as Ritalin (methylphenidate). Since these medications stimulate the sympathetic nervous system, they possess the potential to influence cardiac function. The aims of this study were a) to assess autonomic nervous system functioning in 20 children with ADHD, as compared to controls, and to examine the effects of focussed attention and sympathomimetic medication on this system, b) to investigate cardiac functioning in 20 children with ADHD, as compared to controls, and to examine the effects of sympathomimetic medication on this system and c) to assess EEG functioning in children with ADHD, as compared to controls, and to examine the effects of sympathomimetic medication on this functioning. Children with ADHD were tested while they were stimulant-free and during a period in which they were on stimulant medication, while controls were tested once. Autonomic nervous system activity of the children was assessed at baseline and during focussed attention by means of heart rate variability (HRV) and skin conductivity. Attention was evoked by means of a program on the BioGraph Infiniti biofeedback apparatus, which is used specifically to train ADHD individuals to increase their attentive abilities. HRV was determined by time-domain, frequency-domain and Poincaré analysis of RR interval data. Skin conductivity was determined by BioGraph Infiniti biofeedback apparatus. Cardiac functioning of the children was assessed at baseline by means of blood pressure recordings and electrocardiograms (ECGs). Blood pressure was measured by means of a stethoscope and mercurial sphygmomanometer. ECGs were obtained by means of a Schiller CardioLaptop AT-110 ECG recorder using the standard 12-lead cable positioning for a resting ECG and parameters measured included HR, RR, QT, JT, QTc, JTc, QTd, JTd, QTcd and JTcd. EEG values were determined at baseline and during focussed attention by means of BioGraph Infiniti biofeedback apparatus. EEG values measured in this study included theta/beta ratios, theta/SMR ratios and thalpha, low alpha and high alpha power. The main findings of this study are that: <ul> <li>Stimulant-free ADHD children show a parasympathetic dominance of the sympathovagal balance relative to controls.</li> <li>Methylphenidate usage shifts the autonomic balance of children with ADHD towards normal levels; however a normal autonomic balance is not reached.</li> <li>Stimulant-free ADHD children exhibit a shift in the sympathovagal balance towards the sympathetic nervous system from baseline to focussed attention; however, methylphenidate abolishes this shift.</li> <li>Methylphenidate usage does not, in general, cause QTc or JTc prolongation but it may cause QTc or JTc prolongation in susceptible individuals.</li> <li>Children with ADHD can not be differentiated from normal children on the basis of theta/beta ratios, theta/SMR ratios or alpha power.</li> <li>Methylphenidate increases the level of centering in children with ADHD.</li> <li>Stimulant-free ADHD children display an alpha block from baseline to focussed attention; however, methylphenidate abolishes this alpha block.</li></ul> Copyright / Dissertation (MSc)--University of Pretoria, 2009. / Physiology / unrestricted