Talks and Conference Presentations
Cognitive Neuroscience Society
12th Annual Meeting
April 9-12, 2005
New York, New York
Unconscious Word Processing: Differential Activation Based on Word Category and Imageability
Michele T. Diaz1,2 and Gregory McCarthy1,2,3,4
A briefly exposed visual stimulus may not be consciously perceived if it is preceded and followed by a dissimilar visual pattern, or mask. Despite the subject’s lack of awareness, prior behavioral studies have shown that such masked stimuli nevertheless engage domain specific processes. For example, a masked word can speed the recognition of a subsequent related word, suggesting that processing of the masked word was sufficient to activate its semantic representation. In a previous study conducted by our group using functional magnetic resonance imaging (fMRI) and masking, we demonstrated that masked words, but not masked nonwords, elicited activation in a distributed network of left hemisphere brain regions. Here, we further investigated the processing of masked words and nonwords using fMRI by incorporating additional stimuli (masked content words of high and low imageability, masked function words, and masked nonwords). Subjects viewed a continuous stream of masked stimuli while performing an unrelated detection task, in which they were asked to make a response to a visible colored nonword stimulus (e.g., %%%%%%). The task ensured participant engagement, while the masked nonwords controlled for perceptual and orthographic processing. Participants were naïve to the purpose of the experiment and both subjective and objective testing indicated that they did not consciously perceive words, nonwords, or their constituent letters. A random effects analysis indicated that left anterior and posterior middle temporal gyri differentiated words based on imageability, while postcentral gyrus differentiated function words from content words.
Modulatory Effect of Emotion on Brain Activity Associated with Working Memory Operations: Event-Related fMRI Evidence for Affective-Cognitive Interactions
Florin Dolcos1 & Gregory McCarthy1,2
Although the neural mechanisms underlying the beneficial effect of emotion on cognitive functions (e.g., episodic memory) have been extensively investigated, the neural correlates of the detrimental effect of emotion are largely unknown. Here, we investigate the effect of emotional and non-emotional distracters on the neural mechanisms associated with working memory operations.
Differential effects of ambiguity and risk upon brain systems for decision making
Scott A. Huettel1,2, Evan M. Gordon1, Brent T. Warner1, Michael L. Platt3, and C. Jill Stowe4
Many decisions are made under limited information about potential outcomes. When two or more outcomes are possible, with knowable probabilities, decisions are made under risk. Conversely, decisions made without knowledge of outcome probabilities are made under ambiguity. The distinction between risk and ambiguity has been long debated within the economics literature (see Knight, 1921). In the current study, we investigated using functional magnetic resonance imaging (fMRI) whether risk and ambiguity evoke distinct patterns of neural activity during decision making.
Subjects participated in two sessions (one behavioral and one fMRI) of choices between pairs of monetary gambles. Each gamble showed one or more probabilistic rewards (displayed as a pie chart or “spinner”). Three gamble types were used: Ambiguous, Certain, and Risky. These gambles could be arranged in four possible pairings: Ambiguous/Certain (AC), Ambiguous/Risky (AR), Risky/Certain (RC), or Risky/Risky (RR).
Unconscious Face Processing Evokes Activity in the Right Anterior Fusiform Gyrus
James P. Morris1, Kevin A. Pelphrey1, and Gregory McCarthy1,2
Functional magnetic resonance imaging (fMRI) and field potential recordings from subdural electrodes have revealed focal regions of the fusiform gyrus (FFG) that respond to faces but not other objects. Field potential recordings have indicated that these face-specific processes are relatively immune to task manipulations, suggesting that face processing is invoked automatically. In contrast, both PET and fMRI neuroimaging studies have indicated that face activation is strongly influenced by attention and task demands. We hypothesized that these neuroimaging studies may be integrating activity over a large temporal window, and thus may be sensitive to sustained and recurrent activation evoked by task-related and strategic processing. Masking provides the ability to test for automatic processes by eliminating conscious perception and thus strategic processing. In visual masking, a stimulus is presented for a brief duration and is preceded and followed by a dissimilar visual pattern. Here, using event-related fMRI at 4T, we investigated brain activity in response to viewing masked and unmasked faces and objects.
Perception of Dynamic Changes in Facial Expressions of Emotion in Autism
Kevin Pelphrey1,2, James P. Morris1, Elizabeth J. Carter1, Gregory McCarthy1, Kevin S. LaBar3
Impairments in several aspects of face processing are striking features of autism (see Pelphrey et al., 2004, for a review). For example, studies of visual scanpaths indicate that people with autism spend less time looking at the eyes when viewing faces (Klin et al., 2002; Pelphrey et al., 2002). They also have difficulty identifying emotional characteristics of posed facial expressions (Adolphs et al., 2001; Pelphrey et al., 2002). Despite extensive behavioral descriptions of face processing abnormalities in autism, identification of the underlying biological mechanisms remains a critical and largely unmet challenge. Cognitive neuroscientists have started to explore the social brain in adults with autism. Functional neuroimaging studies have reported abnormal activity in components of the human face processing system, including the fusiform gyrus (FFG; e.g., Schultz et al., 2000), posterior superior temporal sulcus (STS; e.g., Pelphrey et al., 2005), and amygdala (AMY; e.g., Baron- Cohen et al., 1999). One limitation of the existing literature is the common use of static, posed snapshots of faces. These stimuli are relatively ineffective in eliciting physiological reactions and do not contain the dynamic facial information displayed in human social interaction. Here we sought to characterize the neural circuitry associated with the dynamic perception of facial affect and identity in individuals with and without autism. Building upon a prior study in neurologically normal adults (LaBar et al., 2003), we compared brain activity to dynamic and static facial expressions in adolescents and adults with and without high-functioning autism using an eventrelated functional magnetic resonance imaging (fMRI) design and three classes of face stimuli: emotion morphs, identity morphs, and static images.
Executive Function and Emotional Processing in Major Depression
Lihong Wang1, Kevin S. LaBar 2,Mark Z. Rosenthal3,Moria Smoski3, Thomas Lynch3, Gregory McCarthy1,4
Neuropsychiatric studies of major depressive disorder (MDD) have identified deficits in executive function and emotional processing. A model proposed as the neural basis for executive function and emotional processing posits that a dorsal system including the dorsal prefrontal cortex and dorsal cingulate gyrus subserves executive function and a ventral system including the amygdala, anterior insula and orbital cortex subserves emotional processing. Neuroimaging studies of MDD have shown abnormally elevated resting cerebral blood flow (CBF) in the ventral system and decreased CBF in the dorsal system. However there is less knowledge on how the ventral and dorsal systems functionally interact in MDD during processing an executive function and emotional task. To address this issue, we acquired functional magnetic resonance imaging (fMRI) in MDD patients and healthy controls during an emotional oddball distracter task. The emotional oddball distracter task required subjects to detect infrequent circle targets among a stream of frequent rectangle standards while task-irrelevant negative emotional and neutral distracting pictures were intermittently presented. Our previous studies in normal controls showed that attentional targets activated the dorsal system (the dorsal prefrontal cortex, the cingulated gyrus and supramarginal gyrus) and the sad distracters activated the ventral system (the amygdala, orbital frontal cortex and the inferior frontal gyrus). Our current study revealed that, compared to controls, the MDD patients showed higher activation in ventral system evoked by the sad distracters. The MDD patients also showed lower activation in the dorsal system by the attentional target, confirming alteration of function within the ventral and dorsal systems in MDD.
Orienting to Unattended Auditory Novelty is Resource-limited
Günes Yücel1, Christopher M. Petty1, Gregory McCarthy1,3, and Aysenil Belger1,2
The ability to detect novel stimuli in the environment is of great biological significance for survival. A strong argument has been put forth for the automatic nature of the neural process of unattended auditory stimuli, suggesting that involuntary auditory attention evoked by unattended novel sounds is not influenced by the current focus of attention. Recent studies have associated auditory involuntary attention shifts with fronto-temporal networks, which also appear to contribute to the generation of the mismatch negativity (MMN) event-related potential (ERP) component (Alho, 1995; Escera et al., 2000). While the temporal cortical contribution has been suggested to represent the early detection of unattended auditory deviant events, frontal sources have been suggested to reflect a signal to trigger a shift of attention towards the initially unattended stimuli (Näätänen, 1992). Whether detection of unattended salient events is altered by the availability of attentional resources has not been established. We used functional magnetic resonance imaging (fMRI) to examine the automaticity of these activations, their modulation by attentional shifts, and the neuroanatomical distribution of any attentional effects upon novelty detection using a dual-task design that controls carefully available attentional resources while simultaneously probing with task irrelevant stimuli (Wickens, 1976; Wickens et al., 1983).