At her post-doctoral position at Georgetown, our PhD alumnus Yuqi Liu has just published a fascinating paper in the Proceedings of the National Academy of Science, in which she examined action representations in individuals born without hands. It’s a very interesting paper and worth your time to read.
Where do people feel a touch when their hand is not where they see it? In the classic rubber hand illusion, people feel touch on the seen rubber hand when it is brushed in synchrony with their unseen actual hand. But does the actual hand still influence tactile perception?
Using the mirror box illusion, we found that when there was spatial mismatch between visual and proprioceptive information of hand position, the perceived location of tactile stimuli on the skin surface was systematically biased toward the proprioceptively-defined hand position compared to baseline. These results provide evidence that the actual hand position exerts influence on tactile localization, adding to past findings that information from external space affects tactile localization in somatotopic space. You can read it here.
We are delighted to welcome three new members to the lab.
Pushpita Bhattacharyya is a new PhD student who received her undergraduate degree from the University of California – San Diego. While working with Dr. V.S. Ramachandran, she examined grapheme-color synesthesia in Bengali. She plans to continue this research and expand to studying mirror-touch synesthesia.
Luisa Raigosa Posada is a new 4+1 student. She comes with a Master of Music degree in clarinet performance and a BS in Neuroscience from the University of Delaware. She will be working on neuroimaging projects – specifically using multi-voxel pattern analysis (MVPA) and representational similarity analysis (RSA) to examine multisensory integration and representations of tactile space.
Riwa Safa is a new PhD student who received her undergraduate degree from the American University of Beirut. Her previous research examined the relationship between reading direction and face perception. She is working on visuoproprioceptive integration, with a focus on evidence from individuals with stroke.
Our new case study has been published in Neuropsychologia. We report an individual with subcortical damage who had excellent detection of light touch on the contralesional hand. However, his tactile localization on the contralesional hand was severely impaired, with his responses clustering on the left side of his hand.
Interestingly, “side” depended on the position and orientation of his hand. Regardless of whether his hand was positioned palm-up or palm-down, his errors were always on the left side of the hand relative to the participant’s viewpoint (i.e. towards the 5th finger with palm down, towards the thumb with palm up). When the hand was turned 90 degrees, his errors were made towards the left side of the hand in a hand-centered frame of reference.
This provides strong evidence for a dissociation of tactile detection and localization, shows that body position can modulate tactile localization, and provides evidence for hand-centered representations for touch. You can read the manuscript here.
We would like to welcome two new members to the lab – Elisabetta Ambron and Anupama Nair. Elisabetta Ambron is a post-doctoral fellow who received her Ph.D. at the University of Edinburgh, and was recently a post-doc at the University of Pennsylvania. She will be studying body representations, focusing on research with brain-damaged individuals. Anupama Nair is a new graduate student who received her B.A. at St. Xavier’s College and received her M.Sc. at the University of Amsterdam. After working on synesthesia and neuroimaging at the University of Michigan and UT-Dallas, she now begins her career as a graduate student in our lab.
We are very happy to announce that we’ve been awarded with a new NSF grant! In a collaboration with Jen Semrau (Kinesiology and Applied Physiology), Hyosub Kim (Physical Therapy) and Fabrizio Sergi (Biomedical Engineering), we plan to study proprioception and multisensory integration in stroke survivors. We will also use robotics and adaptive algorithms to develop individualized rehabilitation protocols for improving sensorimotor function.
We recently published a paper in Acta Psychologica with recent undergraduate Patrick Reyes and two collaborators at the University of Edinburgh, Elena Gherri and Nik Theodoropoulos. In it, we found novel evidence for an externally-based, hand-centered tactile Simon effect, and that it varied based on salience.
Two additional notes on this paper. First, this was our first preregistered paper, and all data and scripts can be found on OSF. Many thanks to Patrick for all his work on the analyses and maintaining the OSF site for this project. Preregistration was fun, and we’re looking forward to doing more of this. Second, this collaboration occurred by chance, as I saw Dr. Gherri giving a presentation on a very similar project. We thought this would be an excellent opportunity to join forces and collaborate, resulting in this paper and additional collaborations in the future.
Unfortunately, we have to say goodbye to our undergraduates who are leaving the lab after graduation. Patrick Reyes is moving on to Stanford to be an RA in Dr. Jeanne Tsai’s Culture and Emotion lab. Cathy Nadar is moving to Penn to start an RA position in Dr. Russell Epstein’s lab studying spatial navigation and scene perception. Finally, Julia Tortu is moving to NYC and taking a gap year. We are proud of all of your accomplishments, and will miss all of you!
We’ve just published a new paper in Cortex. Working with Steve Jax at Moss Rehab and H. Branch Coslett at the University of Pennsylvania, we report an interesting case of an individual with a small tumor resection in right posterior intraparietal sulcus (pIPS). First, we found that her deficit occurred for either limb and was only seen for targets left of fixation, suggesting that pIPS encodes reach locations in an eye-centered reference frame. Second, contrasting previous accounts of optic ataxia, we found that she was better at immediate versus delayed reaching. Finally, although she has no damage to occipital cortex, we found a clear perceptual deficit, as she was poor at detecting changes in stimulus position left of fixation.
Here’s a quick review of papers published in the lab over the last six months.
First, graduate student Yuqi Liu published a paper in Cognition, examining whether congruence in separate frames of reference contribute differently in multisensory integration. Using the mirror box, Yuqi had participants make synchronous or asynchronous tapping movements in the same or opposing postures, manipulating whether the movements were congruent or incongruent in an external frame of reference (i.e. movements going in the same direction) or a motor-based frame of reference (i.e. coordinated flexion/extension). She found increased illusory shift and more ownership of the mirror hand when movements were externally vs. motorically congruent, providing evidence that information re: crossmodal congruency is represented in different frames of reference. For more, see this Twitter thread.
Second, we’ve published two TMS papers with our collaborators at Penn. In a paper with Priyanka Shah-Basak published in Neuropsychologia, we presented participants with a task where participants had to judge whether a line was bisected centrally, or to the left/right of the line center. Importantly, these lines were presented centrally, or to the left/right of the viewer to separate the effects of TMS on viewer-centered or stimulus-centered processes. We found that TMS of right superior temporal gyrus (STG) disrupted performance resulting in additional errors in which participants reported that the right side of the line was longer (i.e. “neglecting” the left side of the line). Importantly, this was observed regardless of line position relative to the subject, suggesting that STG plays a role in stimulus-centered, but not viewer-centered processing.
In a separate TMS study with Elisabetta Ambron published in the Journal of Cognitive Neuroscience, we found that visual magnification of the hand influences motor evoked potentials using TMS. When seeing the hand magnified, we found larger MEPs for the magnified hand (but not the opposite, not magnified hand), and that more areas of motor cortex were active as a function of TMS stimulation.
Finally, in work with our collaborators at the University of Nevada-Reno, we published a review paper in Consciousness and Cognition on object shape and motion processing in human dorsal cortex.