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The effects of auditory attention measured from human electrocorticograms. (Fri, 30 May 2008 19:56:36 +0000)

The effects of auditory attention measured from human electrocorticograms.

    Clinical Neurophysiology , Volume 117 , Issue 3 , Pages 504 - 521
    M . Neelon , J . Williams , P . Garell

Abstract

Objective

A central question in auditory electrophysiology has been whether selective attention can modulate exogenous components of the scalp-recorded N1 (the ‘N1 effect’). Intracranial electrocorticograms were used in the current work to investigate this issue in greater anatomical detail.

Methods

Data were recorded from subdural electrodes placed across temporal cortex in 6 patient-volunteers undergoing diagnostic procedures for medically intractable epilepsy. Patients performed a dichotic listening task in which they alternately attended to a series of tones presented to both ears (mean ISI 800ms) by responding to rare frequency deviants.

Results

Effects of attention were measured on the largest negative and positive waveform deflections observed between 70 and 220ms post-stimulus for stimuli presented contralateral to grid location. Peak deflections were most often recorded from the upper bank of the posterior superior temporal gyrus at approximately 89 and 173ms on average (labeled N90stg and P170stg, respectively). Selective attention had little effect on peak latencies but significantly increased the N90stg for 3 subjects, increased the P170stg for two subjects, and decreased the P170stg for two other subjects.

Conclusions

Selective auditory attention can modulate neural response in auditory cortex.

Significance

The effects of attention on the scalp-recorded N1 component may arise in part from the enhancement of exogenous responses in temporal cortex.
   

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Diving bell & the butterfly (Mon, 03 Dec 2007 22:53:45 +0000)

A new movie, “The Diving Bell and the Butterfly,” has recently been released detailing the life of Jean-Dominique Bauby, the former editor of Elle magazine, who suffered from locked-in syndrome. Using his only remaining movement, blinking his eye, he wrote the book of the same name over a period of months, letter by letter. This story is often cited as one of the inspirations for brain-computer interface research, and our BCI program is working on developing new communications systems, such as integrating Dasher and BCI2000. The video link shows an example of how a BCI could be used by a person with locked-in syndrome for writing.

Dasher Video

Media: video/mpeg (17423028 bytes)

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Be a Subject! Scheduling What is a BCI? More Info New Participants

What Is a BCI?

"BCI" is an acronym for brain-computer interface. There are several other names that are often used as well, such as brain-machine interface, thought-translation device, or (more generally) neuroprosthetic, which all generally describe the same type of system. As these names suggest, a BCI is an interface, or connection, between a person's brain and a computer. This interface is designed so that it does not rely on a person's normal output pathways, such as the arm and hands, for interacting with the external environment. A BCI removes the intermediate steps of the spinal cord, peripheral nervous system, and musculature, which is particularly important in individuals who may not have full use of their motor abilities. Therefore, the goal of most BCI systems is to provide a platform for a person with motor disabilities to interact and communicate more effectively with their environment and other people.

A BCI generally consists of three parts: a signal acquisition module, a signal classification/translation module, and an application module. The signal acquisition module is made up of the brain signal, the amplifier and digital signal processor, and a computer. The brain signal can be collected in many different ways, including electroencephalogram (EEG), electrocorticogram (ECoG), micro-electrodes, or magnetoencephalogram (MEG), to name a few. EEG and ECoG are the most commonly used in human research, and are what are used in the NITRO lab.

Once the signals are recorded into the computer, a variety of computations are done on the brain signals to determine what the subject is attempting to do. For example, when a person makes a movement (or THINKS about making a movement), there is a change in the brain signal, which is recorded on one or more electrodes. The computer learns what these changes are, and how to translate these into a device command. The final step in a BCI is the application. The application uses the control signals from the brain to drive an external system, such as a computer cursor or wheelchair. This output in turn allows the user to fine-tune their behavior, which we call "closing the loop." When the loop is closed, the user can see the effects that changes in their brain-waves has on the output, allowing them to adjust and adapt their behavior much more quickly.

The goals of our BCI research are: