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Chris Rorden's Neuropsychology Lab
Attention and perception
- Our senses flood the brain with an overwhelming amount of information – how do we select the relevant information? Clinical syndromes such as spatial neglect (where individuals ignore information on their left side) provide insight into how the brain achieves this.
Rorden and Karnath (2010) :: We describe a simple and robust measure for evaluating the severity of spatial neglect. Our algorithm is included in our free software.
Speech and language
- Communication is invaluable for sharing information, planning and coordinating actions in a group. Human language is quantitatively and qualitatively a quantum leap from that seen in other species. Cognitive neuroscience is able to employ new techniques to understand language. This work will help reveal who we are, and may help people who have suffered profound communication difficulties following brain injury.
Fridriksson et al. (2010) :: People who have suffered left hemisphere injury often have difficulty naming common objects. Here we identify the regions where the level of brain activity predicts performance on these tasks. This work may be helpful in developing therapies that attempt to stimulate these areas (such as our work with tDCS).
- Each of or techniques requires us to develop sensitive behavioral tasks: for example in an fMRI study of time perception we will want to compare tasks where the person makes temporal judgments (e.g. which item appeared first) to perceptually identical tasks where the participant judges a different domain (for example the shape of the items). We have extensive skill in designing and implementing these tasks.
Rorden C et al (2012) :: Allocentric neglect strongly associated with egocentric neglect. Neuropsychologia. 50:1151-7.
functional Magnetic Resonance Imaging :: fMRI
- MRI scans use radio signals to take pictures of the brain. fMRI is a type of MRI scan that is is sensitive to oxygenation concentration, allowing us to infer brain function. Typically, we have people perform simple tasks in the scanner while we collect fMRI scans. We have used this technique to identify the brain areas involved with speech and perception. In addition, we have used fMRI to examine recovery from brain injury.
Davis et al. (2009) :: How does an umpire determine which came first: the ball hitting the glove or the foot hitting the plate? We found that the temporoparietal junction was one of the regions that was specifically activated when making temporal order judgments.
Lesion-behavior mapping :: LBM
- Lesion behavior mapping associates the location of brain injury with the resulting symptoms. For example, we use this technique to identify the brain injuries that result in speech impairment. We can also use this technique to identify the best targets for neurosurgery.
Bonilha et al. (2007) :: Surgery can stop seizures seen in epilepsy. This is crucial, as recurrent seizures can lead to cognitive problems.We found removal of both the entorhinal cortex and hippocampus were predictive of a successful surgery.
Transcranial Direct Current Stimulation :: tDCS
- tDCS applies weak electrical currents to the scalp. It appears that tDCS can induce subtle changes in brain activity, with regions near the positive electrode showing slightly increased firing rates, whereas regions under the negative electrode show small decreases in firing rate. Curiously, these changes seem to persist for many minutes after the stimulation ends. Because this technique is very safe and inexpensive, this technique offers potential for the helping people recover from brain injury as well as revealing the function of the healthy brain. We have devised methods for double-blind testing of tDCS (where neither the participant nor the experimenter knows the type of stimulation used) to investigate this mysterious but promising technique.
Baker et al. (2010) :: We worked with individuals who had diffiicult naming objects following brain injury. We found that tDCS applied to the frontal cortex resulted in small but reliable improvements in naming.
Transcranial Magnetic Stimulation :: TMS
- TMS uses a brief magnetic pulse to stimulate parts of the brain near the TMS coil. The region of stimulation is relatively focused. By introducing TMS pulses while participants are conducting a task we can determine if the stimulated region is crucially responsible for performance on that task. Our TMS systems are located in the brain stimulation labs.
Rorden et al. (2008) :: We found that stimulating the left frontal cortex interferes with individual’s ability to discriminate between silent films showing speech movements, but not silent videos showing gurning face movements. This is consistent with ‘mirror neuron’ models of speech, which suggest that the regions involved with observing speech are harnessed to produce speech.