John McDowall

Preserved implicit learning on both the serial reaction time task and artificial grammar in patients with Parkinson's disease.

Thirteen nondemented patients with Parkinsons disease (PD) were compared with age-matched controls on two standard tests of implicit learning. A verbal version of the Serial Reaction Time (SRT) task was used to assess sequence learning and an artificial grammar (AG) task assessed perceptual learning. It was predicted that PD patients would show implicit learning on the AG task but not the SRT task, as motor sequence learning is thought to be reliant on the basal ganglia, which is damaged in PD. Patients with PD demonstrated implicit learning on both tasks. In light of these unexpected results the research on SRT learning in PD is reconsidered, and some possible explanations for the sometimes conflicting results of PD patient samples on the SRT task are considered. Four factors which merit further study in this regard are the degree to which the SRT task relies on overt motor responses, the effects of frontal lobe dysfunction upon implicit sequence learning, the effects of cerebellar degeneration, and the degree to which the illness itself has advanced.

Anxiety and depression: Why and how to measure their separate effects

It is well recognized that depression and anxiety are closely associated, but nonetheless, they may be associated with distinct causes and consequences. For example, anxiety and depression are associated with different effects on information processing. This paper argues that experiments should not study anxiety or depression in isolation, but should measure both variables. It is argued that this methodological step is both important and commonly overlooked. Even when both depression and anxiety are measured, methodological difficulties can confuse their effects. Common difficulties in choice of measures and in participant selection criteria are discussed, and recommendations are made for overcoming them. The argument is made drawing from illustrations within the experimental cognitive literature, but conclusions and recommendations are equally applicable outside this area.

Impaired higher order implicit sequence learning on the verbal version of the serial reaction time task in patients with Parkinson's disease

Although neuroimaging studies have strongly implicated basal ganglia involvement in implicit sequence learning, serial reaction time (SRT) studies with Parkinsons disease (PD) patients have yielded mixed results. The present research sought to examine the ability of people with PD to implicitly learn sequences with different sequential structures and to objectively assess explicit knowledge. A version of the SRT task that reduces motor demands was used to compare 19 patients with PD but not dementia and 37 matched controls. PD patients showed less implicit sequence-specific learning for both sequences and reduced response time improvement over sequential trials for the more complex sequence. A closer examination revealed that the deficit involved higher order sequential associations as well as the learning of pairwise information.

Implicit and explicit memory in pregnant women: An analysis of data-driven and conceptually driven processes

A study by Brindle, Brown, Brown, Griffith, and Turner (1991), reported that pregnant women showed impaired implicit memory (as measured by a stem completion task) in the presence of intact explicit memory. The present study was an attempt to replicate and extend this finding by employing a read/generate encoding manipulation across data-driven (word fragment completion and graphemic cued recall) and conceptually driven (semantic cued recall and category generation) tests. A total of 64 women (32 pregnant) were tested on both data-driven and conceptually driven tasks either directly or indirectly. No differences emerged between pregnant subjects and non-pregnant controls across tasks. Subjects experiencing their first pregnancy did report their memory in the previous 2 weeks as being considerably worse than normal.

Visible markers of brain injury influence attributions for adolescents’ behaviour

Primary objective: Experiments investigated whether attributions for a brain-injured persons behaviours were affected by markers of injury. People misattribute behaviours that result from brain injury to personality or life stages (e.g. adolescence), particularly when there are no visible markers of the injury. Research design: Scenarios presented a photograph of an adolescent boy, who either wore or did not wear a head bandage. The boy was described as suffering a brain injury and showing four changes in his behaviour, relating to sleep, anger, self-confidence and motivation. Methods and procedures: For each behaviour, students (n = 100) rated attributions to the brain injury and adolescence. Outcomes and results: When there was no bandage, participants attributed the behaviours to adolescence more than brain injury, whereas with the head bandage they invoked both causes equally. Conclusions: When actions resulting from brain injury are attributed to causes other than the injury, this misattribution hinders accurate diagnosis and treatment. Data on effects of injury and individual levels of pre-morbid behaviours lead to accurate attributions.

Indirect learning of event sequences: the effects of divided attention and stimulus continuity

In a serial reaction time (SRT) task, the learning curve is sleeper when the stimuli are presented in a repeating sequential manner rather than in random order (Nissen & Bullemer, 1987). This is true even when subjects report being unaware of the presence of the repeating sequence. The present study examines the nature of this learning under conditions designed to reduce attentional resources and to disrupt the continuity of stimuli. In the first three experiments, subjects were trained in the SRT task, with or without the addition of a secondary tone counting task, and with repeating or non-repeating sequences. The results suggest that some sequence learning occurred despite the presence of a secondary task. Experiment 4 examined the extent of sequence learning when the inter-stimulus interval was varied between trials. The overall results suggest that despite reduced attentional allocation and discontinuous stimulus presentation, some sequence learning occurs. This result supports other work suggesting a dissociation between learning when measured explicitly, and when assessed through performance indicators.

Implicit memory and depression: An analysis of perceptual and conceptual processes

A small number of studies have reported impaired explicit memory and intact implicit memory performance in participants classified as depressed. In the present study we examined this finding taking account of the distinction between datadriven and conceptually driven processing. The performance of participants diagnosed with depression was examined on implicit and explicit memory tasks which were designed to tap either predominantly perceptual or conceptual processes. Depressed participants demonstrated performance deficits on both the implicit and explicit conceptual tasks (category association and free recall, respectively) but showed intact performance in the implicit perceptual task (word-fragment completion). These results suggest that people with severe depression show deficits in conceptual processing and that this deficit occurs under both explicit and implicit task instructions.

Attributions for behaviours of persons with brain injury: The role of perceived severity and time since injury

Primary objective: The experiment determined first whether visible markers of brain injury shape judgements of severity of injury and time since injury; and secondly whether these two judgements predict attributions for undesirable actions performed by an adolescent with brain-injury. Research design: Scenarios presented a photograph of an adolescent, in one condition with a head scar and in a second condition with no scar. The adolescent was described as having suffered a brain injury and showing four behaviour changes, concerning sleep, anger, self-confidence and motivation. Methods and procedures: For each behaviour, students (n= 101) rated attributions to the brain injury and adolescence and estimated severity of injury and time since injury. Outcomes and results: With no scar, participants attributed the behaviours to adolescence more than brain injury, whereas with the scar they invoked both causes equally. With the scar they rated severity higher and time since injury shorter; severity predicted participants’ attributions for the behaviours. Conclusions: Visible markers of injury such as scars are spurious indicators of severity but they shape judgements of severity and attributions for actions of persons with brain injury. These results inform more accurate diagnosis and treatment for actions resulting from brain injury.

Effects of encoding instructions on recall and recognition in Korsakoff patients

Abstract Korsakoff subjects and alcoholic controls examined words in a word list under one of three encoding instructions: (1) non-semantic, that is, detecting the presence or absence of the letter “e” in each word; (2) semantic, that is, determining whether a word could fit into a particular sentence, or not; and (3) no encoding instructions. Retention was measured by a free recall procedure (Experiment 1) and by a forced choice recognition procedure (Experiment 2). The results support the hypothesis that Korsakoff subjects are able to semantically encode verbal stimuli without specific instructions to do so.

To Resolve or Not to Resolve

Abstract Trauma workers may be at risk of secondary traumatic stress (STS) through indirect exposure to traumatic material, especially if they have experienced personal trauma. This is the first study to ask whether past trauma resolution influences STS and was examined in 64 volunteer crisis workers, a greatly ignored population. Those with non-resolved personal trauma had higher scores on an STS measure than volunteers whose trauma histories were resolved, while the latter showed less STS than the sample as a whole. STS was unrelated to volunteer experience, exposure to victims, or the type of cases found most distressing, indicating that accepted STS risk factors may not apply to volunteers. Findings have resounding implications for the popular view of trauma history as an STS risk factor: this may double as both a significant peril and a protection, depending on whether the past trauma is resolved.