David J. M. Kraemer

Musical imagery: Sound of silence activates auditory cortex

Auditory imagery occurs when one mentally rehearses telephone numbers or has a song ‘on the brain’ — it is the subjective experience of hearing in the absence of auditory stimulation, and is useful for investigating aspects of human cognition. Here we use functional magnetic resonance imaging to identify and characterize the neural substrates that support unprompted auditory imagery and find that auditory and visual imagery seem to obey similar basic neural principles.

Frontopolar cortex mediates abstract integration in analogy

Integration of abstractly similar relations during analogical reasoning was investigated using functional magnetic resonance imaging. Activation elicited by an analogical reasoning task that required both complex working memory and integration of abstractly similar relations was compared to activation elicited by a non-analogical task that required complex working memory in the absence of abstract relational integration. A left-sided region of the frontal pole of the brain (BA 9/10) was selectively active for the abstract relational integration component of analogical reasoning. Analogical reasoning also engaged a left-sided network of parieto-frontal regions. Activity in this network during analogical reasoning is hypothesized to reflect categorical alignment of individual component terms that make up analogies. This parieto-frontal network was also engaged by the complex control task, which involved explicit categorization, but not by a simpler control task, which did not involve categorization. We hypothesize that frontopolar cortex mediates abstract relational integration in complex reasoning while parieto-frontal regions mediate working memory processes, including manipulation of terms for the purpose of categorical alignment, that facilitate this integration.

Connecting Long Distance: Semantic Distance in Analogical Reasoning Modulates Frontopolar Cortex Activity

Solving problems often requires seeing new connections between concepts or events that seemed unrelated at first. Innovative solutions of this kind depend on analogical reasoning, a relational reasoning process that involves mapping similarities between concepts. Brain-based evidence has implicated the frontal pole of the brain as important for analogical mapping. Separately, cognitive research has identified semantic distance as a key characteristic of the kind of analogical mapping that can support innovation (i.e., identifying similarities across greater semantic distance reveals connections that support more innovative solutions and models). However, the neural substrates of semantically distant analogical mapping are not well understood. Here, we used functional magnetic resonance imaging (fMRI) to measure brain activity during an analogical reasoning task, in which we parametrically varied the semantic distance between the items in the analogies. Semantic distance was derived quantitatively from latent semantic analysis. Across 23 participants, activity in an a priori region of interest (ROI) in left frontopolar cortex covaried parametrically with increasing semantic distance, even after removing effects of task difficulty. This ROI was centered on a functional peak that we previously associated with analogical mapping. To our knowledge, these data represent a first empirical characterization of how the brain mediates semantically distant analogical mapping.

Dissociable substrates for body motion and physical experience in the human action observation network

Observation of human actions recruits a well‐defined network of brain regions, yet the purpose of this action observation network (AON) remains under debate. Some authors contend that this network has developed to respond specifically to observation of human actions. Conversely, others suggest that this network responds in a similar manner to actions prompted by human and non‐human cues, and that one’s familiarity with the action is the critical factor that drives this network. Previous studies investigating human and non‐human action cues often confound novelty and stimulus form. Here, we used a dance‐learning paradigm to assess AON activity during observation of trained and untrained dance cues where a human model was present or absent. Results show that individual components of the AON respond differently to the human form and to dance training. The bilateral superior temporal cortex responds preferentially to videos with a human present, regardless of training experience. Conversely, the right ventral premotor cortex responds more strongly when observing sequences that had been trained, regardless of the presence of a human. Our findings suggest that the AON comprises separate and dissociable components for motor planning and observing other people’s actions.

Neural Correlates of Creativity in Analogical Reasoning

Brain-based evidence has implicated the frontal pole of the brain as important for analogical mapping. Separately, cognitive research has identified semantic distance as a key determinant of the creativity of analogical mapping (i.e., more distant analogies are generally more creative). Here, we used functional magnetic resonance imaging to assess brain activity during an analogy generation task in which we varied the semantic distance of analogical mapping (as derived quantitatively from a latent semantic analysis). Data indicated that activity within an a priori region of interest in left frontopolar cortex covaried parametrically with increasing semantic distance, even after removing effects of task difficulty. Results implicate increased recruitment of frontopolar cortex as a mechanism for integrating semantically distant information to generate solutions in creative analogical reasoning.

The Neural Correlates of Visual and Verbal Cognitive Styles

It has long been thought that propensities for visual or verbal learning styles influence how children acquire knowledge successfully and how adults reason in everyday life. There is no direct evidence to date, however, linking these cognitive styles to specific neural systems. In the present study, visual and verbal cognitive styles are measured by self-report survey, and cognitive abilities are measured by scored tests of visual and verbal skills. Specifically, we administered the Verbalizer–Visualizer Questionnaire (VVQ) and modality-specific subtests of the Wechsler Adult Intelligence Scale (WAIS) to 18 subjects who subsequently participated in a functional magnetic resonance imaging experiment. During the imaging session, participants performed a novel psychological task involving both word-based and picture-based feature matching conditions that was designed to permit the use of either a visual or a verbal processing style during all conditions of the task. Results demonstrated a pattern of activity in modality-specific cortex that distinguished visual from verbal cognitive styles. During the word-based condition, activity in a functionally defined brain region that responded to viewing pictorial stimuli (fusiform gyrus) correlated with self-reported visualizer ratings on the VVQ. In contrast, activity in a phonologically related brain region (supramarginal gyrus) correlated with the verbalizer dimension of the VVQ during the picture-based condition. Scores from the WAIS subtests did not reliably correlate with brain activity in either of these regions. These findings suggest that modality-specific cortical activity underlies processing in visual and verbal cognitive styles.

Color, context, and cognitive style: Variations in color knowledge retrieval as a function of task and subject variables

Neuroimaging tests of sensorimotor theories of semantic memory hinge on the extent to which similar activation patterns are observed during perception and retrieval of objects or object properties. The present study was motivated by the hypothesis that some of the seeming discrepancies across studies reflect flexibility in the systems responsible for conceptual and perceptual processing of color. Specifically, we test the hypothesis that retrieval of color knowledge can be influenced by both context (a task variable) and individual differences in cognitive style (a subject variable). In Experiment 1, we provide fMRI evidence for differential activity during color knowledge retrieval by having subjects perform a verbal task, in which context encouraged subjects to retrieve more- or less-detailed information about the colors of named common objects in a blocked experimental design. In the left fusiform, we found more activity during retrieval of more- versus less-detailed color knowledge. We also assessed preference for verbal or visual cognitive style, finding that brain activity in the left lingual gyrus significantly correlated with preference for a visual cognitive style. We replicated many of these effects in Experiment 2, in which stimuli were presented more quickly, in a random order, and in the auditory modality. This illustration of some of the factors that can influence color knowledge retrieval leads to the conclusion that tests of conceptual and perceptual overlap must consider variation in both of these processes.

A Gene–Brain–Cognition Pathway: Prefrontal Activity Mediates the Effect of COMT on Cognitive Control and IQ

A core thesis of cognitive neurogenetic research is that genetic effects on cognitive ability are mediated by specific neural functions, however, demonstrating neural mediation has proved elusive. Pairwise relationships between genetic variation and brain function have yielded heterogeneous findings to date. This heterogeneity indicates that a multiple mediator modeling approach may be useful to account for complex relationships involving function at multiple brain regions. This is relevant not only for characterizing healthy cognition but for modeling the complex neural pathways by which disease-related genetic effects are transmitted to disordered cognitive phenotypes in psychiatric illness. Here, in 160 genotyped functional magnetic resonance imaging participants, we used a multiple mediator model to test a gene-brain-cognition pathway by which activity in 4 prefrontal brain regions mediates the effects of catechol-O-methyltransferase (COMT) gene on cognitive control and IQ. Results provide evidence for gene-brain-cognition mediation and help delineate a pathway by which gene expression contributes to intelligence.

Cognitive style, cortical stimulation, and the conversion hypothesis

What does it mean to have a “verbal cognitive style?” We adopt the view that a cognitive style represents a cognitive strategy, and we posit the conversion hypothesis – the notion that individuals with a proclivity for the verbal cognitive style tend to code nonverbal information into the verbal domain. Here we used repetitive transcranial magnetic stimulation (rTMS) to disrupt this hypothesized verbal conversion strategy. Following our previous research implicating left supramarginal gyrus (SMG) in the verbal cognitive style, we used an fMRI paradigm to localize left SMG activity for each subject, then these functional peaks became rTMS targets. Left SMG stimulation impaired performance during a task requiring conversion from pictures to verbal labels. The magnitude of this effect was predicted by individuals’ level of verbal cognitive style, supporting the hypothesized role of left SMG in the verbal labeling strategy, and more generally supporting the conversion hypothesis for cognitive styles.

Verbalizing, Visualizing, and Navigating: The Effect of Strategies on Encoding a Large-Scale Virtual Environment.

Using novel virtual cities, we investigated the influence of verbal and visual strategies on the encoding of navigation-relevant information in a large-scale virtual environment. In 2 experiments, participants watched videos of routes through 4 virtual cities and were subsequently tested on their memory for observed landmarks and their ability to make judgments regarding the relative directions of the different landmarks along the route. In the first experiment, self-report questionnaires measuring visual and verbal cognitive styles were administered to examine correlations between cognitive styles, landmark recognition, and judgments of relative direction. Results demonstrate a tradeoff in which the verbal cognitive style is more beneficial for recognizing individual landmarks than for judging relative directions between them, whereas the visual cognitive style is more beneficial for judging relative directions than for landmark recognition. In a second experiment, we manipulated the use of verbal and visual strategies by varying task instructions given to separate groups of participants. Results confirm that a verbal strategy benefits landmark memory, whereas a visual strategy benefits judgments of relative direction. The manipulation of strategy by altering task instructions appears to trump individual differences in cognitive style. Taken together, we find that processing different details during route encoding, whether due to individual proclivities (Experiment 1) or task instructions (Experiment 2), results in benefits for different components of navigation-relevant information. These findings also highlight the value of considering multiple sources of individual differences as part of spatial cognition investigations.