Randy Buckner
Is There A Common Brain Network for Remembering the Past, Envisioning the
Future, and Conceiving the Viewpoints of Others?
We think about the future to explore the consequences of upcoming events
before they happen. Converging data suggest envisioning the future is one
member of a larger class of related forms of self-projection that includes
remembering, conceiving the viewpoint of others (theory of mind), and
navigation. All emerge in development at about the same age and share a
similar core functional anatomy. In particular, frontal and medial temporal
systems traditionally associated with planning and episodic memory are
components of the shared network. Recent imaging data further suggest that
activity increases during passive states and lapses in attention (the
default mode) likely associate with the same core anatomy raising the
possibility that we spend much of our time considering the future and
conceiving alternative perspectives. This bias to be in a processing mode
that shifts our perception from the present to alternative, simulated
perspectives has far-reaching cognitive and physiological consequences
including (possibly) setting the stage for the development of Alzheimer's
disease.
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Barbara Shinn-Cunningham
How attention influences what we hear
In everyday settings, multiple events compete for our limited processing resources, vying for our attention. For instance, in a crowded party, you can choose whether to attend to your friend telling that same tired story you've heard sixteen times, or to listen in on the juicy story unfolding between the couple on your left... In the vision community, the role of attention on perception has been the focus of much study. In contrast, much less is known about the rules governing attention in the auditory domain. Motivated from work on selective attention in vision, work in my lab is exploring the role of attention in complex auditory scenes. I will review evidence that attention modulates competition between simultaneous auditory objects, much as it does for visual objects. Moreover, just as in vision, we find that attention is influenced both by top-down influences (what do you want to hear?) and bottom-up stimulus properties (what sound "pops out" of the mixture?). I will also highlight differences between the visual and auditory senses that influence how attention influences perception. Our work underscores the importance of understanding how perceptual auditory objects are formed and what acoustic cues enable object formation, which we believe is a critical stage for enabling effective selective auditory attention.
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Justin Vincent
Spontaneously emerging templates of mind
Traditional studies of the mind involved the presentation of stimuli and
the observation of behavioral or neuronal responses. However, most of the
brain~Rs metabolic activity is devoted to ongoing neuronal signaling that is not
clearly associated with any particular input or output. I will outline a series
of human and macaque fMRI studies we have performed over the last 2 years that
suggest spontaneous activity is coherently organized in specific spatial
patterns previously associated with sensory, motor, or cognitive phenomenon.
In addition, I will present new data which suggests that these coherent
"templates of mind" persist during unconsciousness induced by anesthesia and
correspond to underlying patterns of anatomical connection. These dynamically
transitioning physiological states may provide the context that determines
neuronal responsiveness to external stimuli as well as the content of the
internal milieu.
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David Feinberg
Mechanism, function, and development of audiovisual associations
We live in a social world where our impressions and interactions with
people are inescapably guided by our ability to take information from
different sensory modalities and integrate that into a coherent
representation of the world. The most intriguing set of questions in
this domain comes from cases where information transmitted through
sights and sounds are incongruent. For example, we are often surprised
by the way someone looks if we have only spoken to them on the
telephone. Also, we often mishear what people are saying; and instead
of processing what is said as incoherent, we perceive different words
than what is said. Here I present these two topics as different sides
to the same coin: how does visual perception (e.g. feature-based vs.
configural processing) influence what we hear; and how does auditory
perception (e.g. associations between voice pitch, vocal-tract length
and body size) influence what we see? To demonstrate how visual
perception influences what we hear, I present preliminary data from an
experiment on audiovisual fusion (the McGurk effect) using different
face types (e.g. adults, infants, animals, shapes, inversions, Thatcher
illusions) revealing that often, but not always, the cognitive processes
underlying audiovisual fusion are consistent with those underlying the
processing of still face images. To demonstrate how auditory perception
influences what we see, I present published data from adult studies and
preliminary data from infant studies on body size perception via
acoustic properties of the voice. Here I will demonstrate that although
adults are often found to use inappropriate acoustic cues to body size,
these associations are either domain or task specific and most likely
learned after the age of 4 months.
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Howard Eichenbaum
The Comparative Neurobiology of Recollection
Do animals have the capacity for conscious recollection? What brain
circuitry supports this ability? I will outline recent evidence from
our studies on rats, as well as findings from on monkeys and humans,
bearing on these questions. My analyses focus on defining features
of recollection that can be examined in animals as well as humans.
These features include the representation of events as items in the
context in which they were experienced, the representation of
episodes as sequences of events, and the ability to link memories and
solve novel problems based on inferences from memory. I will outline
evidence that animals exhibit each of these forms of representation,
that the capacity for each depends on the hippocampus, and that
neurons in the hippocampus encode experiences in terms of these types
of representation. In addition, I will review evidence about the
neural circuitry of the hippocampal system that gives rise to these
features of recollection.
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Arash Afraz
Microstimulation of inferotemporal cortex influences face categorization
The inferior temporal cortex (IT) of primates is thought to be the final
visual area in the ventral stream of cortical areas responsible for object
recognition. Single IT neurons respond selectively to highly complex visual
stimuli such as faces. However, a direct causal link between the activity of
face selective neurons and face perception has never been demonstrated. In
the present study we artificially activated small clusters of IT neurons by
means of electrical microstimulation while monkeys performed a
categorization task, judging whether noisy visual images belonged to face
or non-face categories. Prior to this task, the selectivity profile of the
stimulated locus and its neighboring cortical sites along each recording
track was determined in a passive fixation paradigm. Total of 86 sites along
lower bank of STS and area TE were stimulated in two male macaque monkeys.
Electrical stimulation (50ms duration of 50uA, 200Hz biphasic pulses) was
applied randomly during stimulus presentation, 0-50ms, 50-100ms, or 100-150ms
after
the image onset. In 25% of trials no electrical stimulation was applied. The
effect of stimulation was measured in terms of shift in monkeys&apos
psychometric function in the categorization task. Microstimulation of
face-selective sites, but not other sites, strongly biased the monkeys&apos
decisions toward face category. Magnitude of the effect depended upon the
degree of face selectivity of the stimulation site, the size of the
stimulated cluster of face-selective neurons, and the exact timing of
microstimulation. Our results establish for the first time a causal
relationship between the activity of face-selective neurons and face
perception.
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Gina Kuperberg
Neural Routes to Comprehension: Insights from electrophysiology and fMRI
I will present a series of studies examining the neural basis of human comprehension. I will present evidence that comprehending the meaning of simple, active written sentences as well as of visual real-world events (depicted in short, silent movie-clips) engages two distinct but interactive brain systems: a semantic memory-based stream that links incoming information with existing information stored in semantic memory, and a semantic algorithmic stream that computes relationships between people, objects and actions to determine the structure of verbal and non-verbal events. Our studies using event-related potentials (ERPs) suggest that these neural mechanisms can be temporally dissociated in the brain, and our studies using functional MRI (fMRI) suggest that they can be neuroanatomically dissociated. I will propose that the balanced operation of these two brain systems allows for comprehension that is efficient and yet adaptive. Moreover, I will illustrate how imbalances in activity between these streams can lead to comprehension abnormalities in a variety of neurocognitive disorders, with particular reference to schizophrenia.
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Chris Chabris
Individual Differences in Cognition: The Law of General Intelligence, and
Beyond
Cognitive psychologists typically study the species-universal architecture of the human mind. In any given study, however, a large fraction of the total measured variance is accounted by differences among the participants, rather than among the experimental conditions. For over a century, research has consistently shown that individuals who perform well on one cognitive task tend to perform well on other tasks. Positive correlation among cognitive test scores is observed so ubiquitously that it can be regarded as a behavioral law -- the "Law of General Intelligence." In the first part of this talk, I will present evidence that general intelligence is found in animal species as well as in humans, and that it is a biological trait grounded in neural mechanisms of information processing efficiency and cognitive control. In the second part, I will argue that a full understanding of individual differences in human cognition must go beyond general intelligence to incorporate both special cognitive abilities and "cognitive traits," or characteristics of cognition that do not reflect "ability" per se. I will present data suggesting that (1) the ability to recognize faces may be a special ability, relatively unconnected to general intelligence; (2) individuals’ preferences for spatial- and object-based visualization strategies are separate dimensions of cognitive style that predict the performance of collaborative teams; and (3) one's level of confidence in decision-making is a stable meta-cognitive trait that may be independent of decision quality or general intelligence. The talk will conclude with a brief discussion of how cognitive neuroscience approaches can be used to further our understanding of the mechanisms underlying individual differences.
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Thomas McKeeff
Temporal Limitations of Visual Object Processing
The visual system can convert a retinal image into a meaningful perceptual
representation so rapidly that viewers rarely experience any delay perceiving objects
in the environment. However, when an object is surrounded by similar items, such as
finding a friend in a crowd or a book on a bookshelf, recognition is delayed,
demonstrating a pronounced processing limitation of the visual system. Here, using a
combination of behavioral psychophysics and functional neuroimaging (fMRI), the
factors and neural mechanisms that influence temporal processing limitations for
object recognition were explored. In all studies, subjects discriminated
pre-specified target pairs, embedded in a rapid serial visual presentation (RSVP)
sequence of distractor items (i.e. faces, houses, sine wave gratings, line drawings).
Decreasing the target/distractor visual similarity and increasing stimulus
familiarity lead to a behavioral increase in the temporal processing capacity for
sequences of objects, however, effects were not found manipulating stimulus
complexity. This effect of target/distractor visual similarity was further tested
using objects of expertise, namely cars in car experts. There was a decrease in the
temporal processing capacity when subjects had expertise with both stimulus
categories (faces and cars in car experts) compared to car novices, suggesting that
the speed of perceptual processing and possible competition for cognitive resources
is influenced by visual expertise with different object categories. Using fMRI,
temporal tuning functions of retinotopic visual areas and object-selective areas were
calculated to determine the possible cortical locus of temporal processing
bottlenecks. Results show a progressive loss in the temporal processing capacity of
the visual system as information is transferred from early visual areas to higher
areas. Object-selective areas also appear tuned to the total number of objects
presented, not simply the number of preferred stimuli. Also, directing spatial
attention to one of two sequences increased the tuning of intermediate and higher
visual areas responding to the attended stimuli, however, the shift was weak. It
appears that temporal limitations in vision lies in part in intrinsic temporal tuning
limitations of visual areas.
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Thomas Carlson
Computational Neuroimaging of Face Recognition
How does the brain construct a mental representation of an object? In this talk, I will present a series of studies that apply computational methods to functional neuroimaging data to examine how the brain represents information about objects, and how these representations relate to our perception. I will first present a critical analysis of predictive mapping methods, now more popularly referred to as decoding or mind reading, and show how these methods can provide new insights into the contentious debate about the categorical representations of objects. I will then discuss a second study that uses theoretical information response functions to show how different visual areas represent information about objects. Lastly, I will present a third study that examines how the representation of an object in lateral occipital areas relates to our conscious perception.
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Fiery Cushman
The Origins of Moral Principles
How do humans develop moral principles, and what determines the content of these
principles? In a series of studies, we explore these questions by targeting three
distinctions that play a role in shaping moral judgments: the distinction between
actions and omissions, the distinction between means and side effects, and the
distinction between proximal and distal events. Evidence suggests that
representations of the causal role and intent of an agent in bringing about a harmful
event mediates the role of these three distinctions on moral judgment. The structure
of this mediating role is unexpected, however, calling into question both previous
psychological theories of moral judgment as well as the moral justifications that
subjects provide for their judgments. Specifically, what seems to matter in judging
the wrongness of an action is not the harm it causes, but rather the harm it is
anticipated to cause. This finding is dually informative, providing evidence that
many explicit folk-theories of morality are post-hoc rationalizations of intuitive
judgments, and also providing a new perspective on the cognitive basis of these
intuitive judgments.
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