Thesis (M.S.)--Auburn University, 2005. / Abstract. Includes bibliographical references.

Thesis (Ph. D.)--Auburn University, 2009. / Abstract. Vita. Includes bibliographical references (p. 68-75).

The reticular-activating hypofrontality model of acute exercise (RAH) predicts exercise-induced hypoactivity in frontal cortex which mediates executive function. Connors Continuous Performance Test (CCPT) was used to investigate changes in executive function during- and post treadmill running in healthy volunteers (n=30, 15 male). In a randomized order, subjects performed the CCPT at rest, during low- (LI; 63% maximal heart rate; MHR) and moderate intensity (MI; 75% MHR). Separately, subjects then performed isocalorifically matched exercise bouts of LI, MI and high intensity interval training (HIT) consisting of 4x4 min with 90% MHR and 3 min recovery at 60-70% MHR. Repeated measures ANOVAs revealed main effects of exercise intensity for reaction time RT during- (p≤0.001) and post exercise (p≤0.0001). Subsequent analyses showed an overall increase of RT during exercise compared to rest (p≤0.005). RT decreased significantly from rest to post exercise levels in an exercise intensity dependent, linear fashion (p≤0.0001). Commission errors showed a non significant linear trend to increase both during (p=0.057), and post exercise (p=0.052) as a function of intensity. In a follow up study, we sought to relate observed exercise effects to frontal cortex activity through the use of transcranial direct current stimulation (tDCS) (n=4) and transcranial magnetic stimulation (TMS) over the dorsolateral prefrontal cortex (DLPFC). Prior to TMS stimulation cortical excitability was estimated post running through motor-evoked potentials (MEP) elicited from the primary motor cortex (M1) induced by single burst TMS and measured in the first dorsal interosseous (FDI) muscle using electromyography. At rest, inhibitory cathodal tDCS with left DLPFC cathode and right supraorbital anode led to improved reaction time and increased amount of commission errors, whereas anodal stimulatory tDCS in the immediate post exercise period was unable to recover the post exercise effect. Continuous theta burst stimulation over the left DLPFC post running further impaired inhibitory control and facilitated reaction time. Different findings during- and after- exercise suggests that potential contributing mechanisms such as computational and metabolic factors may be differentially active during these respective conditions. Furthermore, the fact that an inhibitory TMS protocol pronounced the post running effects even more and that we were able to mimic the reported RAH effects at rest with inhibitory frontal tDCS, but observed different patterns during exercise, suggests that the latter state cannot be fully explained by reducing activity in the left frontal cortex alone. Failure to modify the after exercise effect with stimulatory tDCS also supports an interplay of different factors and might emphasize the strong, robust effects of exercise that cannot simply be attenuated by current application. Increases in MEP post running for 35min paired with the observed performance decrements imply an excited state of M1 and might serve as an explanatory cross-link to central fatigue suggesting that a hypofrontal state might enhance the motor cortical drive to activate muscles.

Research on the Berard Auditory Integration Training method has shown improvement in the regulation of attention, activity and impulsivity of children whose auditory system have been re-trained. Anecdotal reports have found improvements in sleeping patterns, balance, allergies, eyesight, eating patterns, depression and other seemingly unrelated physiological states. During the Auditory Integration Training (AIT) procedure dynamic music, with a wide range of frequencies, is processed through a system of filters in the AIT device. The volume and tone of the music is constantly and randomly modulated. The researcher explored Berard AIT as a possible intervention for learners between the ages of six and twelve years, who experienced problems with sustained attention and who have difficulty in shifting their attention from task to task. The aim was to investigate if Berard AIT method would enable the learner to stay calm, relaxed yet alert, with focused attention and thus concentration with appropriate reflection before action. An experimental quantative study, with a pretest-posttest control group design, was conducted to investigate the effect that Berard Auditory Integration Training has on learners with attention problems. Checklists and different measurements were conducted before the training started and repeated three months after the training was completed, to monitor if any change in the way that the learners pay attention, occurred the case group of ten learners was compared with ten learners in a control group who did not initially receive the intervention. Although the results of the post-tests varied amongst the learners, most learners in the experimental group experienced a statistical significant increase in attention control and a reduction in behavioural problems by the third month following the listening sessions. / Thesis (M.Ed.), North-West University, Vaal Triangle Campus, 2010

Research on the Berard Auditory Integration Training method has shown improvement in the regulation of attention, activity and impulsivity of children whose auditory system have been re-trained. Anecdotal reports have found improvements in sleeping patterns, balance, allergies, eyesight, eating patterns, depression and other seemingly unrelated physiological states. During the Auditory Integration Training (AIT) procedure dynamic music, with a wide range of frequencies, is processed through a system of filters in the AIT device. The volume and tone of the music is constantly and randomly modulated. The researcher explored Berard AIT as a possible intervention for learners between the ages of six and twelve years, who experienced problems with sustained attention and who have difficulty in shifting their attention from task to task. The aim was to investigate if Berard AIT method would enable the learner to stay calm, relaxed yet alert, with focused attention and thus concentration with appropriate reflection before action. An experimental quantative study, with a pretest-posttest control group design, was conducted to investigate the effect that Berard Auditory Integration Training has on learners with attention problems. Checklists and different measurements were conducted before the training started and repeated three months after the training was completed, to monitor if any change in the way that the learners pay attention, occurred the case group of ten learners was compared with ten learners in a control group who did not initially receive the intervention. Although the results of the post-tests varied amongst the learners, most learners in the experimental group experienced a statistical significant increase in attention control and a reduction in behavioural problems by the third month following the listening sessions. / Thesis (M.Ed.), North-West University, Vaal Triangle Campus, 2010

This thesis consisted of experiments designed to explore the construct of attention and investigate the disruptive effects of psychotomimetics, with a specific focus on NMDA antagonists. Phencyclidine (PCP) was administered through a variety of treatment regimens in order to to determine the ability of inducing cognitive-specific disruptions in attentional functioning. The hypothesis that sub-chronic exposure to PCP would result in persistent attentional impairment was tested, using the 5-choice serial reaction time task (5-CSRTT). The 5-CSRTT assesses not only visuospatial attention, but also components of impulsivity, compulsivity, speed of processing and motivation. It was determined that an additional task-related intervention that increased the attentional load was required to elucidate attentional impairment following sub-chronic PCP treatment. The ability of rats to perform the modified version of the 5-CSRTT, known as the 5-choice continuous performance test (5C-CPT), was investigated. The 5C-CPT was implemented to provide a task that may have greater analogy to the human CPT, than the original 5-CSRTT. The consequence of dopaminergic D1 system activation was investigated. It was revealed that D1 partial agonism improved attentional performance in a baseline-dependent manner. Following successful acquisition of the task, it was shown that repeated PCP treatment induced cognitive disruption that was cognitive-specific, and not confounded by generalised response disruption. Furthermore, a partial attenuation of the PCP-induced performance disruption was achieved following administration of the D1 partial agonist, SKF 38393. Moreover, sub-chronic PCP treatment was shown to impair 5C-CPT performance in the drug-free state. However, an additional challenge that further increased the attentional load was needed to elucidate a performance deficit. This highlighted that sustained attention/vigilance is sensitive to persistent impairment following sub-chronic PCP administration in a manner consistent with deficits observed in schizophrenia patients. This prompted the investigation that tested the hypothesis that sub-chronic PCP treatment could induce enduring structural deficits in regions associated with attentional performance. Magnetic resonance imaging (MRI) was conducted, in conjunction with 5-CSRTT and pre-pulse inhibition (PPI). It was revealed that sub-chronic PCP treatment resulted in morphological brain abnormalities in brain regions associated with 5-CSRTT performance. This was coupled with deficits in sustained attentional performance following an increase in attentional load, yet PPI was unaffected. Taken together, these findings suggested sub-chronic PCP treatment impairs attentional functionality, an effect that dissociates between effortful and passive attentional processes.

No description available.

This thesis consisted of experiments designed to explore the construct of attention and investigate the disruptive effects of psychotomimetics, with a specific focus on NMDA antagonists. Phencyclidine (PCP) was administered through a variety of treatment regimens in order to to determine the ability of inducing cognitive-specific disruptions in attentional functioning. The hypothesis that sub-chronic exposure to PCP would result in persistent attentional impairment was tested, using the 5-choice serial reaction time task (5-CSRTT). The 5-CSRTT assesses not only visuospatial attention, but also components of impulsivity, compulsivity, speed of processing and motivation. It was determined that an additional task-related intervention that increased the attentional load was required to elucidate attentional impairment following sub-chronic PCP treatment. The ability of rats to perform the modified version of the 5-CSRTT, known as the 5-choice continuous performance test (5C-CPT), was investigated. The 5C-CPT was implemented to provide a task that may have greater analogy to the human CPT, than the original 5-CSRTT. The consequence of dopaminergic D1 system activation was investigated. It was revealed that D1 partial agonism improved attentional performance in a baseline-dependent manner. Following successful acquisition of the task, it was shown that repeated PCP treatment induced cognitive disruption that was cognitive-specific, and not confounded by generalised response disruption. Furthermore, a partial attenuation of the PCP-induced performance disruption was achieved following administration of the D1 partial agonist, SKF 38393. Moreover, sub-chronic PCP treatment was shown to impair 5C-CPT performance in the drug-free state. However, an additional challenge that further increased the attentional load was needed to elucidate a performance deficit. This highlighted that sustained attention/vigilance is sensitive to persistent impairment following sub-chronic PCP administration in a manner consistent with deficits observed in schizophrenia patients. This prompted the investigation that tested the hypothesis that sub-chronic PCP treatment could induce enduring structural deficits in regions associated with attentional performance. Magnetic resonance imaging (MRI) was conducted, in conjunction with 5-CSRTT and pre-pulse inhibition (PPI). It was revealed that sub-chronic PCP treatment resulted in morphological brain abnormalities in brain regions associated with 5-CSRTT performance. This was coupled with deficits in sustained attentional performance following an increase in attentional load, yet PPI was unaffected. Taken together, these findings suggested sub-chronic PCP treatment impairs attentional functionality, an effect that dissociates between effortful and passive attentional processes.

La maladie de Parkinson (MP) est la deuxième affection neurodégénérative la plus fréquente après la maladie d’Alzheimer. Elle se caractérise par un dysfonctionnement du système des ganglions de la base, en rapport avec une dégénérescence des neurones dopaminergiques de la substance noire compacte. A côté des symptômes moteurs, la MP s’accompagne de troubles cognitifs, en particulier une altération des capacités de sélectivité attentionnelle. Ce déficit attentionnel se traduit par des difficultés à sélectionner les informations pertinentes pour la conduite en cours et peut entraîner des troubles cognitifs légers. L’origine des troubles attentionnels reste imprécise : on ignore s'ils résultent d’une défaillance des mécanismes volontaires d’orientation de l’attention ou d'une perturbation des processus automatiques de capture attentionnelle. Le filtrage sensoriel permet de focaliser notre attention grâce à une sélection des informations pertinentes pour l’action en cours et une inhibition des informations non pertinentes. Il peut être exploré en neurophysiologie par le paradigme d’inhibition par le prepulse (PPI). Ce dernier correspond à l’atténuation de la réponse motrice et corticale suite à la présentation d’un stimulus sursautant (pulse) lorsque celui-ci est précédé de quelques millisecondes d’un stimulus non sursautant (prepulse). Le PPI est influencé par l’attention, son amplitude étant majorée lorsque l’attention est portée volontairement sur le prepulse. L’objectif général était donc de mieux identifier la nature des troubles de la sélectivité attentionnelle dans la MP par un paradigme actif de PPI au cours duquel la réponse corticale au pulse est enregistrée. Nous faisions l’hypothèse que les parkinsoniens présenteraient une inhibition plus faible que les témoins sains. En cas de défaillance de mobilisation volontaire des ressources attentionnelles, l'inhibition de la réponse corticale au pulse devrait être moins importante lorsque les ressources attentionnelles allouées au traitement du prepulse mettent en jeu la mobilisation volontaire de l’attention. A l’inverse, en cas de défaut de capture attentionnelle, l’inhibition de la réponse serait moins importante lorsque le traitement du prepulse implique les processus automatiques de capture.Pour répondre à cet objectif, nous avons dans un premier temps développé et validé un paradigme actif de PPI au cours duquel l’effet de la mobilisation volontaire de l’attention et de la capture attentionnelle sur le processus de filtrage sensoriel a été évalué. Pour ce faire, 26 témoins sains jeunes ont bénéficié d’un électroencéphalogramme à haute résolution tout en réalisant une tâche attentionnelle sur laquelle a été greffé un paradigme actif de PPI. Nous avons recueilli la réponse corticale évoquée et induite par la présentation du pulse. 16 témoins sains âgés, 16 patients parkinsoniens sans trouble cognitif et 16 patients avec troubles cognitifs légers ont bénéficié du même enregistrement au cours de la même tâche attentionnelle. Chez les témoins sains jeunes, nous avons montré que les processus de mobilisation volontaire de l’attention et de capture attentionnelle modulaient de façon différentielle la réponse évoquée et induite par la présentation du pulse. Au cours du vieillissement, nous avons observé une meilleure sensibilité de la réponse corticale induite, ce qui nous a conduit à choisir ce marqueur cortical pour évaluer le filtrage sensoriel dans la MP. Nos résultats montrent une réduction de l’inhibition de la réponse induite chez les parkinsoniens avec troubles cognitifs légers, confirmant la distractibilité. La MP s’accompagne aussi d’une altération dans la génération des oscillations corticales dans la bande de fréquence thêta quand la focalisation de l’attention est engagée. / Parkinson’s disease (PD) is the most frequent neurodegenerative disorder after Alzheimer’s disease. It is characterized by degeneration of dopaminergic neurons in the substantia nigra pars compacta, causing a progressive loss of dopamine neurotransmission within the basal ganglia. Apart from motor symptoms, PD patients have cognitive disorders. Namely, focused attention is impaired and PD patients fail to select task-relevant information, leading sometimes to mild cognitive impairment (MCI). The origin of this impairment is still debated: PD-related selective attention deficit may be due either to a failure of goal-directed or stimulus-driven attention. Sensory gating helps the individuals to selectively allocate their attentional resources to salient stimuli and to inhibit irrelevant information. One of the physiological marker of this process is referred to as prepulse inhibition (PPI). It corresponds to the attenuation of the motor and cortical responses to a startling stimulus (pulse) when a non-startling stimulus (the prepulse) precedes the pulse by few milliseconds. PPI can be modulated by attention, its magnitude being greater after a to-be attended prepulse. Moreover, PPI is mediated by basal ganglia.The main aim of this work was to better identify the mechanisms involved in selective attention deficits in PD. We used an active PPI paradigm and recorded the cortical response to the pulse. We assumed that PD patients would exhibit a lower inhibition of the cortical response than healthy controls. If attention deficits in PD are related to an impairment of goal-directed attention, PD patients would exhibit lower inhibition after a to-be attended prepulse than in the other conditions. At the opposite, if it is due to a failure of stimulus-driven attention, inhibition would be lower after a prepulse which involuntarily captures attention than in the other conditions.In order to reach this objective, we have first developed and validated a new active PPI paradigm in order to investigate the role of goal-directed and stimulus-driven attention on sensory-cognitive gating. To this end, high resolution electroencephalogram was recorded in 26 young healthy subjects. They performed a selective attention task combined with an active PPI paradigm and the auditory-evoked and induced cortical response to the pulse was recorded. Then, the same procedure was administered in 16 elderly healthy subjects, 16 PD patients without MCI and 16 PD patients with MCI. In young healthy subjects, we found that stimulus-driven and goal-directed attention each had specific effects on the inhibition of the evoked and induced response to the pulse. The investigation of age-related changes on sensory gating revealed that the induced cortical response was more sensitive for assessing age-related changes than the evoked response. Then, we chose this cortical marker to investigate sensory gating in PD. Our results showed that PD patients with MCI exhibit lower inhibition of induced cortical response to the pulse than healthy controls. This finding confirms previous results showing a high distractibility in these patients. Moreover, PD patients exhibit impaired theta synchronization when focused attention was engaged.

No description available.