My main area of research is the investigation of attention mechanisms in the brain using the methods of event-related potential (ERP) recording, eye-tracking, and functional magnetic resonance imaging (fMRI).
A major focus of my research is to understand the interaction between voluntary and involuntary attention. As part of this research, I have used event-related potentials (ERPs) to isolate and track the effects of attentional capture at multiple levels of processing within the brain. We have shown that processing is affected as early as the extrastriate-generated P1 component, and we have identified a component (the “IIN”) that may be related to the disengagement of attention. [Hopfinger & Mangun, 1998; 2001; Hopfinger & Maxwell, 2005; Hopfinger & Ries, 2005].
I have used fMRI to investigate the neural basis of internally-generated, volitional shifts of attention. By investigating voluntary attention without the confound of an external cue, we have provided new evidence for hemispheric asymmetries in the frontal-parietal attentional control network. Specifically, isolating voluntary attention in this way reveals hemispheric asymmetries in attentional control that correspond with the asymmetries seen in unilateral neglect patients. [Hopfinger, Buonocore, & Mangun, 2000; Hopfinger, Camblin & Parks, in press].
A critical aspect of attentional control is how voluntary and involuntary attention interact. Using ERPs, we have shown that attention is not a unitary mechanisms that is simply oriented in different ways; rather, voluntary and involuntary attention appear to involve overlapping, but somewhat separate mechanisms and effects. In addition, we have used ERPs to identify the stages of processing where interactions occur as well as the stages that are clearly dominated by either voluntary or involuntary attention. [Hopfinger & Ries, 2005; Hopfinger & West, 2006]
Using fMRI, we have identified mechanisms of distraction in visual and parietal cortices and we provided new evidence that the appearance of a new object has a unique ability to engage involuntary attention systems in the brain. Furthermore, we found that a critical difference between more versus less distractible subjects was not in the initial sensory processing of the distractor, but rather in the efficiency of the neural systems in the parietal lobe related to disengaging attention. Less distractible subjects were found to engage this system more frequently, and were thus able to use this reorienting system efficiently and effectively when it was most needed. [Kim & Hopfinger, in press].
We have recently proposed a new mechanism for how memory and attention interact. Specifically, we found that long-term item memory has a significant, and non-voluntary, effect on attentional dwell time. Using eye-tracking, we showed that the memory-status of an item significantly affects how long attention remains at that location and how often the eyes return to that location. Critically, participants’ voluntary strategies did not change these effects. We have now extended this research through a series of behavioral experiments using the attentional blink paradigm to demonstrate that memory has a robust, and automatic, effect on attentional dwell time, even when an extended dwell time immediately impairs task performance. Currently, we are using ERPs to investigate the neural basis of the effects of memory on the holding of attention. [Chanon & Hopfinger, 2008; Parks & Hopfinger, 2008].
We have explored the neural mechanisms of social-gaze orienting, in which one’s attention is reflexively oriented to the location being looked at by another person. Recently, we showed that social gaze orienting did not modulate early levels of visual processing (the P1 component) but that facial emotion did (Fichtenholtz et al., 2007). Gaze orienting interacted with emotion at later processing stages (e.g., the P300 component). In a second ERP study (Fichtenholtz et al., in press), we replicated these main results, using fearful versus neutral emotional expressions. We’ve also recently completed two within-subject experiments directly comparing the neural effects of social gaze orienting to voluntary orienting and to involuntary attentional capture. These experiments provide new data dissociating social gaze orienting from the involuntary capture of attention triggered by a salient physical stimulus. Specifically, only involuntary capture modulated the earliest stage of visual processing (P1), and furthermore, the P300 was modulated in opposite directions by these two types of attention (Chanon & Hopfinger, submitted).
I have been collaborating with colleagues to investigate how my research into the basic mechanisms of attention relates to special populations. For example, with Dr. Bruce Bartholow (University of Missouri), we are using ERPs to investigate the neural mechanisms by which alcohol-related stimuli capture the attention of individuals with low-sensitivity to alcohol (subjects who tend to drink more heavily).
With Dr. Peter Gordon, we have been using fMRI to investigate the neural basis of auditory perception and the plasticity of auditory cortex in adults with unilateral hearing loss.
With Drs. David Penn and Amy Pinkham, we have used fMRI to investigate the neural underpinnings of emotional-cognitive processing in individuals with schizophrenia. We showed that the brain regions supporting complex social judgments are significantly less active in individuals with paranoid schizophrenia compared to healthy controls and individuals with schizophrenia without paranoia. In addition, individuals with autism spectrum disorder (ASD) show similar neural activity to those individuals with paranoid schizophrenia. We also showed that the level of activity within the social cognitive network (i.e., amygdala, ventrolateral prefrontal cortex, superior temporal sulcus) can be related to real-world social functioning. (Pinkham, Hopfinger et al., 2008a; 2008b).