Cross-Cultural Differences in Brain Activity of Specific and General Recognition

Results from paper

Results revealed regions in the left fusiform (left circle) and left hippocampus (right circle) emerged when comparing activity for correct same versus correct similar responses across cultures.

A recent publication from Paige, Ksander, Johndro, & Gutchess (Cortex, 2017) of the Aging, Culture, and Cognition Lab at Brandeis University has shed light on how culture affects brain activation when encoding information into memory. Prior work has suggested that culture influences how people perceive the world, including how much perceptual detail (e.g., size, shape, color, etc.) is remembered. It may not be surprising that culture shapes customs or even social interactions, but evidence also suggests that it shapes cognition. Because encoding details into memory necessitates the engagement of additional cognitive resources, comparing across cultures on the specificity of memory offers a glimpse into which processes and types of information are considered important across cultural groups.

Participants who originated from America or East Asia studied photos of everyday items in a magnetic resonance imaging (MRI) scanner and 48 hours later completed a surprise recognition test. The test consisted of same (i.e., previously seen in the scanner), similar (i.e., same name, different features; for example, a coffee mug that is a different shape or color than what the participant saw at encoding), or new photos (i.e., items not previously seen in the scanner) and participants were instructed to respond “same,” “similar,” or “new.”

Unlike other studies, culture did not disproportionately influence behavioral memory performance for specific information. However, East Asians showed greater activation in the left fusiform and left hippocampus relative to Americans for specific (items correctly recognized as same) versus general memory (items correctly recognized as similar). Additional follow-up analyses confirmed this cultural pattern was not driven by differential familiarity with the items across cultures. One possible explanation for this finding is cultural differences in prioritization of high (e.g., fine details, local information) versus low spatial information (e.g., coarser, global information). In the present study, increased activation in the left medial temporal regions for East Asians may be reflective of additional processes needed to encode specific details into memory, reflecting the greater demands of local, high spatial frequency processing. Current work in the lab is addressing this possibility.

Past work has failed to consider how cross-cultural differences can occur at both the behavioral and neural level. The present findings remedy that, suggesting that culture should be considered an individual difference that influences memory specificity and its underlying neural processes.

Paige, L. E., Ksander, J. C., Johndro, H. A., & Gutchess, A. H. (2017). Cross-cultural differences in the neural correlates of specific and general recognition. Cortex91, 250-261.

 

The Amygdala, Fraud and Older Adults

Figure from Zebrowitz-Gutchess paper

Figure 1. Peak amygdala activation as a function of face trustworthiness for older adult participants. Error bars represent standard errors. COPE is the contrast of parameter estimates [high or medium, or low trustworthy faces minus baseline fixation] from which peak values were extracted at the subject-level using FSL featquery. * p < .05.

There is a widespread belief that older adults are more vulnerable to consumer fraud than younger adults. Behavioral evidence supporting this belief is mixed, although there is a reliable tendency for older adults to view faces as more trustworthy than do younger adults.  One study provided supporting neural evidence by demonstrating that older adults failed to show greater amygdala activation to low than high trustworthy faces, in contrast to considerable evidence that younger adults do show this effect. This result is consistent with the argument for greater vulnerability to fraud in older adults, since the amygdala responds to threatening stimuli. More generally, however, the amygdala responds to biologically salient stimuli, and many previous studies of younger adults have shown that this includes not only threatening, low trustworthy faces, but also high trustworthy faces. The Zebrowitz Face Perception Lab therefore included medium trustworthy faces in order to detect separate effects of high trustworthiness and low trustworthiness on amygdala activation in older adults, something that the one previous study of older adults did not do. Consistent with that study we found that older adults did not show stronger amygdala activation to low than high trustworthy faces.  However, they did show stronger amygdala activation to high than to medium trustworthy faces, with a similar trend for low vs medium, although that difference was not strong enough to be confident that it would replicate (See Figure 1).

The fact that older adults did not show greater amygdala activation to low than medium or high trustworthy faces is consistent with the suggestion that older adults may be more vulnerable to fraud. However, an important question is whether vigilant responding to untrustworthy-looking faces could actually protect one from fraud.  Arguing against this possibility is the finding that although younger adults have consistently shown greater amygdala activation to people who look untrustworthy, they do not show greater activation to those who actually cheat.  On the other hand, some evidence indicates that facial appearance does provide valid cues to threat. Face shape not only influenced younger adults’ trust of potential exploiters, but it also proved to be a valid indicator of economic exploitation.  Furthermore, this face shape cue influenced both younger and older adults’ accurate impressions of aggressiveness. To shed further light on neural mechanisms for any age differences in vulnerability to fraud that may exist requires investigating: 1) the sensitivity of neural responses to actual differences in trustworthiness in the domain of economic exploitation, and 2) whether any age differences in those neural responses are related to differential vulnerability to economic exploitation.

Zebrowitz, L.A., Ward, N., Boshyan, J., Gutchess, A., & Hadjikhani, N. (2017).  Older adults’ neural activation in the reward circuit is sensitive to face trustworthiness.  Cognitve, Affective, and Behavioral Neuroscience.

 

 

Communicating Memory Information Between the Hippocampus and Prefrontal Cortex

Jadhav paper full image

The brain has a remarkable capacity to record our daily experiences and recall this stored information to guide our behavior. For example, every time you decide to get a cup of coffee on campus, you immediately know where to go and then step toward your destination. The ability to successfully memorize paths and navigate in the environment is fundamental for animals searching for food (see Illustration), as well as for humans surviving in a complicated environment, especially when you don’t have your smartphone to rely on, but only your brain as the inner GPS! However, how does the brain learn and remember such plans that allow us to get from one place to another?

We know that a structure in brain called the hippocampus plays an important role in encoding and storing memories. The hippocampus is thought to replay remembered experiences during fast, ripple-like brain waves, termed sharp-wave ripples (SWRs), that occur during “down-time” for the brain, i.e., offline periods during sleep and during pauses in active behavior. It has been previously shown by Jadhav and colleagues that selectively disrupting these ripple oscillations using precisely-timed electrical impulses impairs the ability of animals to learn in spatial mazes, suggesting that this “mental replay” is important for navigation and memory (Jadhav et al., 2012, Science). Notably, mental replay is not isolated activity in the hippocampus, but works together with the prefrontal cortex (PFC), the executive center of brain involved in storing memories and making decisions (Jadhav et al., 2016, Neuron). However, exactly how such memory replay supports memory processing in waking and sleep states had remained elusive.

In a new article published in the Journal of Neuroscience (Tang et al., 2017), the Jadhav lab (the team included Neuroscience graduate students Wenbo Tang and Justin Shin) used high-density electrophysiology to record large numbers of neurons in both the hippocampus and prefrontal cortex in both sleep and awake states. They discovered that as rats learned a spatial memory task, the activity in the hippocampal-prefrontal network replayed recent experiences in a precise manner during SWRs that occurred when animals paused from actively exploring the maze. This structured mental replay related to ongoing spatial behavior is ideally suited for storing and retrieving memories to inform decisions. When animals were asleep after exploring the maze, the hippocampal-prefrontal replay, however, appeared “noisy” and mixed. This replay occurring during sleep periods can support the ability of the brain to consolidate memories, by selectively integrating related memories to build a coherent map for long-term storage (see Illustration). These findings show how memory information is communicated between the hippocampus and PFC during ripple oscillations, and indicate that mental replay during sleep and awake states serve distinct roles in memory. These studies collectively provide fundamental knowledge about the neural substrates of memories. They will thus provide important insights into memory deficits that are prevalent in many neurological disorders that involve the hippocampal-prefrontal network, such as Alzheimer’s disease and schizophrenia.

Hippocampal-Prefrontal Reactivation during Learning Is Stronger in Awake Compared with Sleep States. Wenbo Tang, Justin D. Shin, Loren M. Frank and Shantanu P. Jadhav. Journal of Neuroscience 6 December 2017, 37 (49) 11789-11805.

 

Searches for Tenure-Track Faculty in the Sciences, 2017

Brandeis has six open searches for tenure-track faculty in the Division of Science this fall, with the intent to strengthen cross-disciplinary studies across the sciences. We are looking forward to a busy season of intriguing seminars from candidates this winter.

  1. Assistant Professor of Biochemistry. Biochemistry is looking for a creative scientist to establish an independent research program addressing fundamental questions of biological, biochemical, or biophysical mechanism, and who will maintain a strong interest in teaching Biochemistry.
  2. Assistant Professor of Chemistry. Chemistry seeks a creative individual at the assistant professor level for a tenure-track faculty position in physical (especially theoretical/computational) chemistry, materials chemistry, or chemical biology.
  3. Assistant Professor of Computer Science. Computer Science invites applications for a full-time, tenure-track assistant professor, beginning Fall 2018, in the broad area of Machine Learning and Data Science, including but not limited to deep learning, statistical learning, large scale and cloud-based systems for data science, biologically inspired learning systems, and applications of analytics to real-world problems.
  4. Assistant Professor in Soft Matter or Biological Physics. Physics invites applications for the position of tenure-track Assistant Professor beginning in the fall of 2018 in the interdisciplinary areas of biophysics, soft condensed matter physics and biologically inspired material science.
  5. Assistant Professor or Associate Professor in Psychology. Psychology invites applications for a tenure track appointment at the rank of Assistant or Associate Professor, with a specialization in Aging, to start August 2018. They seek an individual with an active human research program in any aspect of aging, including cognitive, social, clinical and health psychology.
  6. Tenure Track Assistant Professor in Applied MathematicsMathematics invites applications for a tenure-track position in applied mathematics at the rank of assistant professor beginning fall 2018. An ideal candidate will be expected to help to build an applied mathematics program within the department, and to interact with other science faculty at Brandeis. Candidates from all areas of applied mathematics will be considered.

Brandeis University is an equal opportunity employer, committed to building a culturally diverse intellectual community, and strongly encourages applications from women and minorities.  Diversity in its student body, staff and faculty is important to Brandeis’ primary mission of providing a quality education.  The search committees are therefore particularly interested in candidates who, through their creative endeavors, teaching and/or service experiences, will increase Brandeis’ reputation for academic excellence and better prepare its students for a pluralistic society.

Sekuler elected to Society of Experimental Psychologists

Robert Sekuler photoLouis and Frances Salvage Professor of Psychology and Professor of Neuroscience Robert Sekuler has been elected a fellow of the Society of Experimental Psychologists.  The society, founded by Edward Titchener in 1904, elects 6 new members annually from among the leading experimentalists in North America. Sekuler and his lab continue to research issues involved with visual perception, visual and auditory memory, and the cognitive process, often using video games in the research process.

Taste and smell are intertwined in the rat brain

A recent paper in Current Biology titled “A Multisensory Network for Olfactory Processing” from the Katz Lab in Psychology tackles the question of where in rat brain the senses of taste and smell are processed, and just how distinct the two senses are. In addition to Katz, authors on the paper include former postdoctoral fellows Joost Maier and Jennifer Li, as well as Neuroscience graduate student Meredith Blankenship.

The paper discusses their finding that the tongue and the nose work together to help you decide what potential foods are actually good to eat. This intimate cooperation leads to an intertwining and interdependence of function; everyone who has had a cold knows that things don’t taste right when the sense of smell is blocked (by snot). They now show that the opposite is true as well–specifically, that the part of the cortex known to be responsible for taste is also required for the sense of smell.

Recordings from taste and olfactory cortex

First, they show that there is a strong neural connection between taste cortex (GC) and olfactory cortex (PC): this connection ensures that information about tastes in the mouth reaches the latter from the former, but also ensures that a constant chatter of action potentials (the language of the brain) flows between the two, even in the total absence of a substance on the tongue. Thus, switching those taste cortex neurons off both removes any evidence of taste information in olfactory cortex AND changes the way olfactory cortex deals with odor information arriving directly from the nose. The result of this impact is striking: a rat utterly fails to recognize a familiar odor when taste cortex is silent; the taste system is a part of the smell system.

The implications of this finding for neuroscience are far-reaching. It suggests a major breakdown of the basic dogma that the different sensory systems, each of which originate in distinct sense organs (the nose for smell, the tongue for taste) process their input independently. In fact, the brain likely doesn’t “see” tastes and smells as separate at all, but as unified parts of holistic objects…FOOD.

Maier JX, Blankenship ML, Li JX, Katz DB. A Multisensory Network for Olfactory Processing. Curr Biol. 2015.

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