The role of the basal ganglia in learning and memory: insight from Parkinson's disease

It has long been known that memory is not a single process. Rather, there are different kinds of memory that are supported by distinct neural systems. This idea stemmed from early findings of dissociable patterns of memory impairments in patients with selective damage to different brain regions. These studies highlighted the role of the basal ganglia in non-declarative memory, such as procedural or habit learning, contrasting it with the known role of the medial temporal lobes in declarative memory. In recent years, major advances across multiple areas of neuroscience have revealed an important role for the basal ganglia in motivation and decision making. These findings have led to new discoveries about the role of the basal ganglia in learning and highlighted the essential role of dopamine in specific forms of learning. Here we review these recent advances with an emphasis on novel discoveries from studies of learning in patients with Parkinson's disease. We discuss how these findings promote the development of current theories away from accounts that emphasize the verbalizability of the contents of memory and towards a focus on the specific computations carried out by distinct brain regions. Finally, we discuss new challenges that arise in the face of accumulating evidence for dynamic and interconnected memory systems that jointly contribute to learning.     

Only self-generated actions create sensori-motor systems in the developing brain

Previous research shows that sensory and motor systems interact during perception, but how these connections among systems are created during development is unknown. The current work exposes young children to novel 'verbs' and objects through either (a) actively exploring the objects or (b) by seeing an experimenter interact with the objects. Results demonstrate that the motor system is recruited during auditory perception only after learning involved self-generated interactions with objects. Action observation itself led to above-baseline activation in one motor region during visual perception, but was still significantly less active than after self-generated action. Therefore, in the developing brain, associations are built upon real-world interactions of body and environment, leading to sensori-motor representations of both objects and words.     

Walk this way: approaching bodies can influence the processing of faces

A highly familiar type of movement occurs whenever a person walks towards you. In the present study, we investigated whether this type of motion has an effect on face processing. We took a range of different 3D head models and placed them on a single, identical 3D body model. The resulting figures were animated to approach the observer. In a first series of experiments, we used a sequential matching task to investigate how the motion of an approaching person affects immediate responses to faces. We compared observers’ responses following approach sequences to their performance with figures walking backwards (receding motion) or remaining still. Observers were significantly faster in responding to a target face that followed an approach sequence, compared to both receding and static primes. In a second series of experiments, we investigated long-term effects of motion using a delayed visual search paradigm. After studying moving or static avatars, observers searched for target faces in static arrays of varying set sizes. Again, observers were faster at responding to faces that had been learned in the context of an approach sequence. Together these results suggest that the context of a moving body influences face processing, and support the hypothesis that our visual system has mechanisms that aid the encoding of behaviourally-relevant and familiar dynamic events.     

Predictors of the change in self-stigma following a single session of group counseling

One of the major obstacles to seeking psychological help is the stigma associated with counseling and therapy. Self-stigma, the fear of losing self-respect or self-esteem as a result of seeking help, is an important factor in the help-seeking process. In the present study, college students meeting a clinical cutoff for psychological symptoms participated in 1 session of group counseling that either contained therapist self-disclosure or did not. In general, participants reported significantly less self-stigma following the session. Working alliance-bond and session depth significantly predicted the change in self-stigma. Furthermore, self-stigma (as well as bond, depth, psychological symptoms, and being female) predicted the intention to seek help following the session. Self-stigma and session depth also predicted interest in continuing with counseling. The therapist self-disclosure condition, however, had no effect on the change in self-stigma, intentions to seek help, or interest in continuing with group counseling.     

Sensori‐motor experience leads to changes in visual processing in the developing brain

Since Broca’s studies on language processing, cortical functional specialization has been considered to be integral to efficient neural processing. A fundamental question in cognitive neuroscience concerns the type of learning that is required for functional specialization to develop. To address this issue with respect to the development of neural specialization for letters, we used functional magnetic resonance imaging (fMRI) to compare brain activation patterns in pre‐school children before and after different letter‐learning conditions: a sensori‐motor group practised printing letters during the learning phase, while the control group practised visual recognition. Results demonstrated an overall left‐hemisphere bias for processing letters in these pre‐literate participants, but, more interestingly, showed enhanced blood oxygen‐level‐dependent activation in the visual association cortex during letter perception only after sensori‐motor (printing) learning. It is concluded that sensori‐motor experience augments processing in the visual system of pre‐school children. The change of activation in these neural circuits provides important evidence that ‘learning‐by‐doing’ can lay the foundation for, and potentially strengthen, the neural systems used for visual letter recognition.     

Understanding suicide terrorism: Premature dismissal of the religious-belief hypothesis

We comment on work by Ginges, Hansen, and Norenzayan (2009), in which they compare two hypotheses for predicting individual support for suicide terrorism: the religious-belief hypothesis and the coalitional-commitment hypothesis. Although we appreciate the evidence provided in support of the coalitional-commitment hypothesis, we argue that their method of testing the religious-belief hypothesis is conceptually flawed, thus calling into question their conclusion that the religious-belief hypothesis has been disconfirmed. In addition to critiquing the methodology implemented by Ginges et al., we provide suggestions on how the religious-belief hypothesis may be properly tested. It is possible that the premature and unwarranted conclusions reached by Ginges et al. may deter researchers from examining the effect of specific religious beliefs on support for terrorism, and we hope that our comments can mitigate this possibility.     

Learning to fail: reoccurring tip-of-the-tongue states

This experiment looked at elicited tip-of-the-tongue (TOT) states to test the hypothesis that making an error once makes people more likely to make it again, via an implicit learning mechanism. We present a methodology that allows us to determine whether error reoccurrences are due to error learning or to the fact that some items tend to pose repeated difficulty to participants. We elicited TOTs by asking participants to supply the word that fitted a given definition. Each time participants indicated that they were experiencing a TOT they were randomly assigned a delay of either 10 or 30 seconds, during which they were asked to keep trying to retrieve the item. After the delay, the correct answer was supplied. We argue that this longer delay in a TOT state amounts to greater implicit learning of the erroneous state. A period of 48 hours later, participants returned to the laboratory and were asked to supply the words for the same definitions as those seen on Day 1. Results showed that TOTs were almost twice as likely to reoccur on words that had elicited a TOT and been followed by a long delay than on those that had been followed by a short delay.     

The moderator effect that wasn't there: statistical problems in ambivalence research

Ambivalence researchers often collapse separate measures of positivity and negativity into a single numerical index of ambivalence and refer to it as objective, operative, or potential ambivalence. The authors argue that this univariate approach to ambivalence models undermines the validity of subsequent statistical analyses because it confounds the effects of the index and its components. To remedy this situation, they demonstrate how the assumptions underlying the indices derived from the conflicting reactions model and similarity-intensity model can be tested using a multivariate approach to ambivalence models. On the basis of computer simulations and reanalyses of published moderator effects, the authors show that the frequently reported moderating influence of ambivalence on attitude effects may be a statistical artifact resulting from unmodeled correlations of positivity and negativity with attitude and the dependent variable. On the basis of extensive power analyses, they conclude that it may be extremely difficult to detect moderator effects of ambivalence in observational data. Therefore, they encourage ambivalence researchers to take an experimental approach to study design and a multivariate approach to data analysis.     

Age-related deficits in reality monitoring of action memories

The authors describe 3 theoretical accounts of age-related increases in falsely remembering that imagined actions were performed (A. K. Thomas & J. B. Bulevich, 2006). To investigate these accounts and further explore age-related changes in reality monitoring of action memories, the authors used a new paradigm in which actions were (a) imagined only, (b) actually performed, or (c) both imagined and performed. Older adults were more likely than younger adults to misremember the source of imagined-only actions, with older adults more often specifying that the action was imagined and also that it was performed. For both age groups, illusions that the actions were only performed decreased as repetitions of the imagined-only events increased. These patterns suggest that both older and younger adults use qualitative characteristics when making reality-monitoring judgments and that repeated imagination produces richer records of both sensory details and cognitive operations. However, sensory information derived from imagination appears to be more similar to that derived from performance for older adults than for younger adults.