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To survive in a complex changing environment humans frequently need to adapt their behaviour incidentally from normal interactions in the environment without any specific intention to learn. Whilst there is a considerable body of research into incidental learning of sequential information there is still fundamental debate regarding its cognitive basis, the associated neural mechanisms and the way in which it is affected by neurological disease. These issues were explored, in normal participants and neurological patients, using manipulations of the Serial Reaction Task [SRT] in which participants gradually learn a stimulus sequence (usually screen locations) after responding to each item by pressing corresponding response buttons. The first two experiments (chapter 3) demonstrate that the specific metric used to quantify learning and the occurrence of highly salient repeat locations may inflate estimates of learning in tasks with increased motor demands. The next three experiments (chapter 4) examine whether a secondary (not directly behaviourally relevant) information source during the SRT facilitates chunking in memory and overall learning. In a spatial SRT task (specified by horizontal location), additional spatial information (vertical location) enhanced learning but a secondary perceptual property (colour) produced a cost. However, in a perceptual SRT a secondary perceptual property (colour) had no effect. The next study demonstrates that impairments of incidental learning in Parkinson’s disease are partially reduced by administration of l-Dopa. Implications for models of striatal function and studies suggesting implicit learning is impaired by l-Dopa are discussed. Finally, the impact of Deep Brain Stimulation of the GPi is investigated in a population known to have only limited cognitive deficits relating to their illness (dystonia). Despite previous reports of impaired intentional learning in participants with a high genetic risk of Dystonia, there was no evidence for any impairment before or after stimulation. Implications across studies and future research directions are also discussed.

The ability to respond rapidly with spatial precision is required in a number of facets of everyday life, whether catching a falling object, reacting to other drivers on a busy freeway or recovering one’s balance following an unexpected perturbation. The sophisticated central nervous system (CNS) control of these reactions is often overlooked until the speed of such reactions becomes delayed, either due to ageing or brain injury, wherein the individual becomes at risk of injury. Surprisingly, little is known regarding the control of these ‘temporally urgent’ movements. Therefore, the primary objectives of this dissertation were to develop an understanding of the control of these movements by exploring the factors that may be involved in the generation of temporally urgent movements in the healthy CNS, locating the areas within the CNS that such modulation occurs and identifying the relative weighted importance of those modulators based on the initial conditions of stimulus delivery. Specific characteristics of stimulus properties, such as intensity and modality were particularly influential in the latency of motor reactions and physiological electrodermal skin responses fluctuated in accordance with input stimulus parameters. Importantly, outcomes from this dissertation identified that rapid reactions likely utilize a CNS network that includes higher cortical regions such as somatosensory cortex and primary motor cortex, which may be modulated by physiological arousal, rather than the solitary involvement of subcortical structures. The findings from this dissertation have important implications for individuals with disordered speed of processing and indicate the potential modifiability of factors that influence reaction time.

Aim The study had the aim to increase knowledge of characteristics possessed by Swedish elite athletes. More specific the level of affect, athlete engagement and reaction time were investigated. A second aim was to test if a reflective training log based on principles from self-regulation could influence these variables.   Questions part one: Baseline What are the level of affect, athlete engagement and reaction time in a sample of Swedish elite athletes? How strong are the correlations between these variables? Questions part two: Intervention Does a self-regulation training log effect athlete engagement, affect or reaction time in Swedish elite athletes? Is there a difference if the reflections are based on either personal strengths or weaknesses? How do the athletes perceive the use of a self-regulation training log? Method/Experiment design The general outline is a randomized controlled trial on a population of Swedish elite athletes using a baseline measurement and an intervention consisting of two experiments (EG1; EG2) and one placebo group (PG). Eligibility criteria for participants were a membership in Sport Campus Sweden (SCS). The data were collected in the participants own home or current location using correspondence by mail/e-mail and a web-based test platform provided by Hogrefe psykologiförlag. A simple 1:1:1 randomization was used for allocation. Only previously tested and validated measurements were used (PANAS; AEQ; CompACT simple RT). 40 athletes performed the baseline registration of reaction time and 32 persons participated in the measurements of affect and athlete engagement. 23 athletes completed all stages of the one month intervention including pre and post-tests. EG1 (reflections on personal weaknesses) N=6; EG2 (reflections on personal strengths) N=8; PG (writing down time spent by watching TV or by the computer as a placebo) N=9.   Result Part 1 showed that Swedish elite athletes outperformed 91 % of a normative sample in reaction time. They were also more stable than 87 % of the norm. Correlation analysis show a strong significant correlation between positive affect and athlete engagement (0.74) (p=0.00). In Part 2 the training log intervention showed no significant results in affect, athlete engagement or reaction time. There were no differences if the reflections were based on personal strengths or weaknesses. In general the athletes perceived the self-regulation training log as rewarding and easy to use.   Conclusions Swedish elite athletes have a superior reaction time compared to a normative sample and are also more stable in their reactions. They experience a high level of positive affect and athlete engagement and these variables are also strongly correlated. A self-regulation training log did not show any results on affect, athlete engagement or reaction time. The training log got positive feedback. Consequences of these findings are discussed. / Syfte Studien har som syfte att utöka kunskapen om specifika egenskaper som svenska elitidrottare besitter. Mer detaljerat undersöks affekt, engagemang och reaktionstid. Vidare är syftet att undersöka om dessa variabler kan påverkas genom att skriva i en självreglerings- och reflektionsinriktad träningsdagbok.   Frågeställningar Del 1: Baslinjeundersökning Var ligger nivån gällande affek, idrottsligt engagemang och reaktionstid hos svenska elitidrottare? Hur starka är korrelationerna mellan dessa variabler? Del 2: Intervention: skriva i en reflektionsinriktad träningsdagbok Kan en träningsdagbok baserad på självreglering påverka affekt, idrottsligt engagemang och reaktionstid hos svenska elitidrottare? Är det skillnader om reflektionerna är baserade på personliga styrkor eller svagheter? Hur upplever elitidrottarna användandet av träningsdagboken? Metod Metoden är en randomiserad kontrollerad experimentell fältstudie på en population av svenska elitidrottare. Studien består av en baslinjeregistrering och en intervention under en månad med två experimentgrupper (EG1;EG2) och en placebogrupp (PG). Urvalskriterium var ett medlemskap i Sport Campus Sweden (SCS). Deltagarna genomförde tester i sitt eget hem eller på sin dåvarande position via brev/mail samt en webbaserad testplattform som tillhandahölls av Hogrefe psykologiförlag. En enkel 1:1:1 randomisering genomfördes. Enbart tidigare validerade frågeformulär samt mätutrustning användes (PANAS; AEQ; CompACT simple RT). 40 deltagare genomförde baslinjeregistreringen av data gällande reaktionstid och 32 deltagare genomförde den första mätningen av affekt och idrottsligt engagemang. Efter avslutad intervention hade 23 deltagare genomfört samtliga för -och eftertest. EG1 (reflektion på svagheter) N=6; EG2 (reflektion på styrkor) N= 8; PG (placebo genom att skriva ner tv-tittande och tid framför datorn) N=9.   Resultat Del 1 visade att elitidrottarna hade en kortare reaktionstid än 91 % av ett normativt snitt av befolkningen i samma åldersgrupp. De var även mer stabila i sina reaktioner än 87 % av normen. En stark och statistisk signifikant korrelation återfanns mellan positiv affekt och idrottsligt engagemang (0.74 )(p=0.00). Del 2 visade att interventionen med en reflekterande träningsdagbok inte gav några signifikanta resultat oavsett om interventionen var baserad på reflektioner gällande personliga styrkor eller svagheter. Idrottarna upplevde generellt träningsdagboken som givande och enkel att använda.   Slutsats Svenska elitidrottare har en överlägsen reaktionstid jämfört med en normalbefolkningsnorm. De är även mer stabila i sina reaktioner samt upplever en hög nivå av positiv affekt och idrottsligt engagemang. Dessa variabler var även starkt signifikant korrelerade.  Träningsdagboken hade ingen signifikant påverkan på upplevelsen av affekt och idrottsligt engagemang eller idrottarnas reaktionstid. Träningsdokumentationen upplevdes i allmänhet som givande. Konsekvenser av dessa resultat diskuteras

The stopping of an earlier intended action is best explained in a race between a go process and a stop process (Logan & Cowan, 1984). The finish line, to which each process races, has been likened to a point of no return, specifically one that marks the onset of a final ballistic (unstoppable) process. Of note is the typical relation of reduced go probabilities and faster go latencies at shorter signal onset asynchronies (SOAs). (The SOA is the time interval between presentation of the go signal and presentation of the stop signal.) We report, in some cases, sub-maximal surface electromyograms (EMGs) at onset when trying to stop a maximal speeded action. These data indicate reduced synaptic drive to reach the motor pools as a result of earlier stopping effects and, as such, hold important implications for a theory of control. First, we interpret these data to suggest that the point of no return is phantom. Sub-maximal EMGs indicate a point in the control stream beyond which some EMG will be later observed but, importantly, they fail to mark the onset of a final ballistic process if, once breached, the same process remains subject to further effects of stopping. The alternative interpretation, however, that of a final ballistic process that receives sub-maximal input which results in sub-maximal output (i.e., EMG onset) cannot be ruled out from these data. We used the Hoffmann (H) reflex to probe further the mechanism of control for stopping a voluntary action. The H-reflex, an involuntary reflex that is taken as an index of spinal control, is relevant to the control of stopping because it is typically facilitated a short time before EMG onset. In other words, it provides a window of control within which a final ballistic process would otherwise be expected to locate. Thus, we interpret the effects of stopping on the H-reflex before EMG onset as strong evidence against a final ballistic process. Second, while the race model can explain the relation between the go probabilities, the go latencies and the SOAs, it fails to explain the sub-maximal EMG onsets that describe that same action in some cases. We submit a mechanism of excitatory-inhibitory interaction at all times up to the motor pool to explain both sets of empirical data. The viability of this theory is demonstrated using computer analyses.

I investigated the effects of probability on visual search. Previous work has shown that people can utilize spatial and sequential probability information to improve their performance on visual attention tasks. My task was a simple visual search in which the target was always present among a field of distractors, and could take one of two colors. The absolute probability of the target being either color was 0.5; however, the conditional probability – the likelihood of a particular color given a particular cue combination – varied from 0.1 to 0.9. I found that participants searched more efficiently for high conditional probability targets and less efficiently for low conditional probability targets. This modulation of efficiency was reduced or abolished when participants were not explicitly informed of the cue-target relationships. After establishing this effect, I investigated its mechanism using eye tracking methods. Early in trials, participants fixated preferentially, but not exclusively, on areas of the screen which contained predominantly stimuli of the color to which they had been cued. As the trial progressed, this color bias shifted to the target color. I conclude that search efficiency is modulated by the conditional probability of target features and that this is a top-down process that benefits from explicit knowledge of the probabilistic relationship between cues and targets, and that the modulation is a result of more efficient eye movements towards stimuli with a greater probability of being the target of search.

The ability to respond rapidly with spatial precision is required in a number of facets of everyday life, whether catching a falling object, reacting to other drivers on a busy freeway or recovering one’s balance following an unexpected perturbation. The sophisticated central nervous system (CNS) control of these reactions is often overlooked until the speed of such reactions becomes delayed, either due to ageing or brain injury, wherein the individual becomes at risk of injury. Surprisingly, little is known regarding the control of these ‘temporally urgent’ movements. Therefore, the primary objectives of this dissertation were to develop an understanding of the control of these movements by exploring the factors that may be involved in the generation of temporally urgent movements in the healthy CNS, locating the areas within the CNS that such modulation occurs and identifying the relative weighted importance of those modulators based on the initial conditions of stimulus delivery. Specific characteristics of stimulus properties, such as intensity and modality were particularly influential in the latency of motor reactions and physiological electrodermal skin responses fluctuated in accordance with input stimulus parameters. Importantly, outcomes from this dissertation identified that rapid reactions likely utilize a CNS network that includes higher cortical regions such as somatosensory cortex and primary motor cortex, which may be modulated by physiological arousal, rather than the solitary involvement of subcortical structures. The findings from this dissertation have important implications for individuals with disordered speed of processing and indicate the potential modifiability of factors that influence reaction time.

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Objective: The purpose of this dissertation was to determine whether measures of reaction time inconsistency (RTI) can be applied clinically to detect cognitive impairment in older adults. Methods: Data were obtained from the Victoria Longitudinal Study (VLS), a longitudinal study of healthy aging, and PREVENT, a multivariate study of risk factors for Alzheimer’s disease. Study 1 examined effects of task complexity and computational approach on the association between RTI and physical and cognitive functioning in participants of the VLS. Study 2 assembled normative data from the VLS and standardized RTI data from an independent VLS cohort against these normative data. Significant Study 1 findings were replicated in Study 2 using the obtained RTI T-Scores, and the clinical utility of results were evaluated using stratum specific likelihood ratios (SSLRs). Study 3 replicated Study 2 analyses in data from PREVENT. Results: Results of Study 1 identified four operationalizations of RTI from a choice reaction task that yielded consistent significant associations with cross-sectional cognitive performance. Consistent associations were not observed between these scores and cognitive change or performance on measures of physical functioning. Study 2 replicated Study 1 findings in an independent sample using RTI T-Scores. SSLRs supported the clinical utility of measures of RTI for detecting prevalent cognitive impairment. Study 3 replicated findings from Study 2, but SSLRs indicated that only low RTI scores yielded associations of sufficient reliability for clinical interpretation. Consistent with Study 1 and Study 2, associations between RTI T-Scores and measures of physical function were nonsignificant. Conclusions: Low RTI T-Scores were shown across two samples to be associated with a clinically meaningful reduction in the odds of cognitive impairment. Further research is needed in order to clarify the utility of high RTI scores for positive prediction of cognitive impairment. / Graduate