Current Doctoral Projects of the IRTG

I: Basic Learning and Memory Processes

Project I-1: Encoding and representation of evaluative information (Contact: Prof. Dirk Wentura)
Research in the group Wentura is concerned with automatic processing of evaluative information. Does processing of evaluative stimuli play a special role in the cognitive apparatus? Will signals of danger be processed preattentively? How do we acquire evaluative connotations? How are evaluative features represented in memory? Accordingly, the field is characterized by experimental paradigms adapted from cognitive psychology which aim at assessing fast, involuntary, possibly unconscious processes, like, for example, the Stroop task, semantic priming, the cuing task, visual search, variants of conditioning procedures as well developments within the field like evaluative priming or the approach-avoidance paradigm. Above that, where appropriate, EEG or eye-tracking is used. Within this overarching topic, two specific research topics (i.e., possible PhD projects) currently are: (1) Learning of evaluative features is typically explored by the evaluative conditioning paradigm. Though it is highly plausible that different shades of positive and negative evaluation are immediately learned (e.g., the differentiation of threat-associated versus sadness-associated negativity), almost every study on evaluative conditioning focuses on learning of mere "pleasantness" or "unpleasantness". It should be explored whether the evaluative conditioning procedure is suited to capture learning of more differentiated connotations. (2) One of the structural demands for human cognitive systems is the need to routinely evaluate the environment for dangers and opportunities. A recurrent theme in this area is the assumed processing advantage for negative (or threatening) stimuli. Based on recent research of the group, these issues should be explored by linking basic research on attentional capture with the field of processing affective stimuli. Although research will be dominantly focusing on behavioral paradigms, the use of eye-tracking is encouraged.

Project I-2: Memory and violated expectancies (Contact: Prof. Axel Mecklinger)
While it is well established that the hippocampus is needed to encode memories for new events and to retrieve information from memory, there is increasing evidence that the striatal dopamine system plays a critical role for declarative memory as well. The mechanisms by which the striatal dopamine system can enhance memory are not yet fully understood. However, this system is likely to play an important role for both, encoding and retrieval. Striatal activation may serve to re-encode previously learnt items due to their expected utility. The striatum may also allow high-utility contextual cues facilitated access to working memory and by this provide a top down signal that biases retrieval towards items with high expected utility in a particular context (e.g., the ticket for the Neil Young concert on the desk that cues a number of nice memories of that concert). The present project will explore the mnemonic consequences of the striatum's ability for marking deviations from what is expected: so-called reward prediction errors. According to this view, participants adjust encoding and retrieval strategies relative to the deviation of an outcome from an expectation and these reward prediction errors in turn can guide the selection of a particular encoding or retrieval strategies. In this project, event-related potentials (ERPs) and brain imaging measures will be used to explore these dopaminergic modulation of memory processes.

Project I-3: Influence of in-group-out-group effects on the acquisition of action knowledge (Contact: Prof. Gisa Aschersleben)
When learning from others, children have to take into account others' competence as models and copy their actions selectively depending on how reliable they are. Research has shown that already young children are selective imitators. Among other characteristics like the model's competence, group membership might also play an important role. Models belonging to the same ethnic group as the child might be judged more reliable and competent as compared to models from a different ethnic group. Thus, in the present study, German and Chinese preschool children will watch German and Chinese models presenting novel actions on objects. We expect children from the same ethnic group as the model to show higher imitation scores than under conditions under which model and child differ with respect to their ethnic group. To study plasticity of action knowledge in development, different age-groups will be tested. In addition, we plan to study the imitation of ethno-typical actions. If children take into account the cultural context of the model, they should preferably imitate those actions which are typical for the cultural context of the model.

Project I-4: Representation of action knowledge in preschoolers (Contact: Prof. Gisa Aschersleben)
In adults, it has been shown that action understanding results from a mechanism that maps an observed action onto representations of that action. In visually guided actions, adults produce anticipatory eye movements that are similar to those produced when an observer analyses an observed action. For example, when subjects observe a block stacking task, the coordination between their gaze and the actor's hand is predictive, rather than reactive, and is highly similar to the gaze-hand coordination when they perform the task themselves. There is first evidence that not only adults but children as well produce predictive eye movements when observing visually guided actions. This is taken as first evidence that anticipatory fixations of action goals indicate the use of action knowledge for prediction. However, it is still unclear whether these anticipatory eye movements obtained in children while observing an action are comparable to those eye movements obtained when the children perform the action themselves. Therefore, in this project, we plan to test preschoolers using the block stacking task in an action observation as well as in an action production task. The eye movements will be assessed by means of an eye tracker. Positive results would indicate that already children implement eye motor programs directed by motor representations of manual actions during action observation.

Project I-5: Visual working memory capacity and its modulation by expertise (Contact: Prof. Hubert Zimmer)
Visual working memory (WM) is considered as temporary storage of information that is no longer in view. Therefore, mainly perceptual characteristics of the perceived stimuli, e.g., their complexity, should influence memory performance. Contrary to this, it has been shown that the familiarity of the stimuli (the participant's expertise with the seen items) also influences performance. The aim of this project is to disclose the mechanisms which cause this WM advantage of familiar items. In a former brain imaging study (Zimmer et al., 2012) we were able to enhance working memory by familiarizing participants with complex visual material (Chinese characters), and this enhancement was associated with reduced activity in the intra-parietal sulcus - a structure that is part of the neural WM network. This neural saving was correlated with the behavioral training gain. The current project should capitalize on this result and deepen our understanding of the basis of training effects in WM. The PhD candidate will use brain imaging and electrophysiological methods to disclose how expertise with the stimuli enhances working memory capacity. Ideally, he or she is already trained in at least one of these neuro-cognitive methods or is highly motivated to learn them.

II: Neurocognitive Plasticity: Individual Dispositions and Cognitive Interventions

Project II-1: Cognitive control training and its transfer to episodic memory (Contact: Prof. Axel Mecklinger)
Cognitive control is defined as a set of mechanisms that allow goal-oriented and context-appropriate behavior. A growing body of research has demonstrated that the brain has a remarkable capacity for plasticity in cognitive control abilities even in adulthood. Notably, the training of cognitive control abilities can lead to performance benefits that extend to untrained tasks and can even modulate the neuronal signatures of cognitive control. This doctoral project aims to explore the transfer of cognitive control training to strategic encoding and retrieval processes in episodic memory and to identify the brain-based principles of this transfer. For example, it is still an open question whether cognitive control training (often implemented via working memory training) also improves the ability to encode information in memory or to set up strategic processes for memory retrieval. Alongside the training of cognitive control abilities, this project will also use neuro-feedback procedures to examine whether revised electrophysiological signatures of cognitive control (frontal theta power and ERP slow waves) show transfer to the behavioral level by improving cognitive control abilities and memory performance.

Project II-2: Association deficits in long-term and short-term memory in old age and their neural underpinnings (Contact: Prof. Hubert Zimmer)
Cognitive aging is characterized by a pronounced decline in episodic memory. Particularly striking is the older adult's association deficit, which is the impairment in remembering links between pieces of information in memory. Sometimes, this is also called a binding deficit. Originally, the association deficit was considered an age-related impairment of long-term memory (for a review see Old & Naveh-Benjamin, 2008) and it was partially seen as consequence of a less efficient hippocampal binding process. Given that the hippocampus was assumed not to be relevant for short-term binding, no comparable deficit was expected in these tasks. In contrast, recent developments suggest that the association deficits in both tasks are similar. It is now claimed that the hippocampus is always needed for binding if binding is complex (Yonelinas, 2013). In this project, it is therefore planned to compare the association deficit in short-term and long-term memory by testing the same participants in both tasks. Behavioral and electrophysiological methods will be used to investigate the similarities between the age-related impairment of binding processes in both memory tasks. Additionally, brain imaging will be used to search for structural correlates of these impairments. The ideal candidate for this project has strong interests in memory and aging research, and he or she is already trained in neuro-cognitive methods or is highly motivated to learn them.

Project II-3: Does impaired relational processing modulate the age-related association deficit and can training on relational processing be used for compensation? (Contact: Prof. Hubert Zimmer and Prof. Wolfang Reith)
The so-called association deficit is an age-related impairment of long-term memory (for a review see Old & Naveh-Benjamin, 2008) and it refers to poor associative memory with preserved item memory. Besides degradation of relevant brain structures, poor relational processing is discussed as reason for this deficit. In two recent studies we could find evidence in support of this idea. First, in a brain imaging study we observed that elderly participants showed reduced activity in the hippocampus and in brain areas devoted to sensory encoding when the encoding demands of picture pairs were high; in contrast, activity was increased in the default network which is related to task-irrelevant processing. We interpret this as an indicator of less encoding activity for these difficult item pairs even though more effort should have been invested. Comparable results were observed in an eye tracking study where we found indicators of reduced relational processing by comparing the fixation pattern between younger and older participants during study. We therefore assume that elderly people adapt their encoding strategies less to the difficulty of the task, probably because they take less proactive control (e.g., Braver, 2012). In the planned PhD project, both techniques (fMRI and eye tracking) should be used to analyze the contribution of reduced relational processing to the age-related association deficit. For this purpose, two types of experiments are intended. Firstly, we will search for correlates of relational processing during study, and secondly, we want to demonstrate that enhancing relational processing by training can (partially) compensate for the association deficit. As training regime we would like to use video games capitalizing on the growing number of studies demonstrating their positive effects on cognition (Bavelier et al., 2012). The PhD project is planned in close cooperation with the Clinic of Diagnostic and Interventional Neuroradiology (Prof. Dr. Reith). In Prof. Reith's group, satellite projects will investigate the same research topics within specific clinical populations using paradigms developed by the PhD candidate. To give an example, Parkinson patients have an insufficient supply of dopamine and there is evidence that proactive control is related to dopamine level. It is therefore possible that these patients show a larger association deficit than age-matched healthy controls. This result would provide indirect support for the executive control hypothesis. Therefore, although the candidate will be mainly supervised by Prof. Zimmer from the Department of Psychology, she or he will spend a part of the time in the clinical context.

Project II-4: The influence of individual differences (task performance level, fluid intelligence, motivational variables) on age-related changes in practice-induced cognitive changes after task-switching training (Contact: Prof. Jutta Kray)
Cognitive training interventions can either enhance (amplification model) or reduce (compensation model) age-related changes in task performance in trained and untrained tasks. Although there is some evidence for the view that task-switching training reduces age-related changes in task performance (e.g., Karbach & Kray, 2009; so the less able benefitted most), less is known about the extent to which other individual differences variables such as fluid intelligence and motivational variables contribute to such training gains and age differences therein. The aim of this project will be to determine the relative impact of these individual differences variables by comparing high and low performing subjects in each age group in understanding the training success in task switching.

Project II-5: The influence of individual differences (performance level) on age-related changes in practice-induced neuronal changes after task-switching training (Contact: Prof. Jutta Kray and Prof. Hubert Zimmer)
The goal of this project will be to identify brain regions that are commonly recruited in trained and untrained transfer tasks and to determine whether brain-activity changes in the trained tasks are predictive of brain activity changes in the untrained transfer tasks. Given that older adults nearly always differ in baseline task performance and given that there is evidence that either decreases or increases of brain activity in the same brain regions can be observed depending on intellectual abilities (high or low performing subjects; for a review, Neubauer & Fink, 2009), individual differences in baseline task performance will be controlled systematically to examine the practice-induced changes in task switching in younger and older adults and their neural correlates.

Project II-6: Intelligence and working memory: Disentangling an intrigate relationship (Contact: Prof. Frank Spinath)
Intelligence and working memory are strongly interrelated. Research focusing on the relationship between fluid intelligence (e.g. measured by matrices tests) and working memory tries to identify how these two constructs influence each other. Recent studies have shown that solving strategies in matrices tests are highly correlated to individual performance scores. However, the link between those solving strategies and working memory remains unclear so far. Therefore, the first goal of this project is to identify and verify individual solving strategies of matrices tests and to disentangle their relationship to working memory. Furthermore, studies investigating the influence of different working memory components on intelligence are rare. Most studies focus on storage and processing functions as the most predictive factor for intelligence. However, further domains such as relational integration and supervision are discussed at this point. Hence, the second goal of this project is to investigate the influence of different working memory domains on intelligence and solving strategies. To answer these questions several matrices tests, working memory batteries and eye tracking paradigms will be applied and discussed in the light of cognitive and differential psychology.

Project II-7: Cortisol as a potential pharmacological booster to reduce reexperiencing symptoms after traumatic experiences - analogue studies (Contact: Prof. Tanja Michael)
Trauma exposure is a major challenge for psychological health worldwide. After experiencing a traumatic event, a significant proportion of the survivors develop posttraumatic stress disorder (PTSD). PTSD is a severe anxiety disorder, which is characterized by maladaptive memory processes. Patients with PTSD suffer from intrusive images of the traumatic event, which retain its vividness and power to evoke distress for decades. Indeed, intrusive memories are considered the hallmark symptom of PTSD, as they cause immense distress and are a strong predictor for the development of PTSD. In fact, there is a consensus within the trauma research community that intrusions are a key factor for comprehending and treating PTSD. Recently, intrusive memories have been linked to glucocorticoids (called cortisol in humans). Cortisol is a stress hormone released from the adrenal cortex that is known to influence memory processes. Administration of cortisol enhances the consolidation of new memories and, most importantly, impairs the retrieval of old memories. In the context of PTSD, the latter effect may counteract the hyper-retrieval of trauma memories. This assumption has received support from a preliminary clinical study showing that intrusions become less frequent after cortisol administration. The present project will focus on the interplay between cortisol and intrusive memories. Using analogue studies we plan to systematically investigate how cortisol levels prior to the traumatic event, during the traumatic event and after the traumatic event influence intrusive memories.

Project II-8: The impact of stress on the consolidation of neutral and emotional episodic memories (Contact: Prof. Tanja Michael and Prof. Axel Mecklinger)
Prior studies have shown that post-encoding stress can protect memories from forgetting by directly facilitating memory consolidation. This kind of memory enhancement is evolutionary adaptive as aversive events and/or stressful situations are better remembered but can also become maladaptive as in the case of posttraumatic stress disorders (PTSD). Recent studies suggest that stress enhances memory strength (as required in tests of recognition memory) and less so memory generation processes which play a critical role in tests such as free recall. Also, stress administered prior to or after encoding exerts differential effects on episodic memory; and the release of stress hormones (cortisol) as well as acute arousal levels are important mediators between stress and episodic memory. However, the impact of stress on emotional and neutral events and the underlying neural mechanisms are still not fully understood. In this project, EEG and ERP measures will be used to explore how stress modulates neutral and emotional aspects of episodic memory at pre- and post encoding stages.