The NIMH is conducting studies aimed at gaining a better understanding of the areas of the
brain that are involved in different types of mental processes. This study will focus on
brain regions involved in visual perception and attention.
Healthy normal volunteers and people who have had a stroke or undergone neurosurgery may be
eligible for this study. Candidates must be 18 years of age or older, They must not have a
history of a psychiatric disorder, including depression, anxiety, psychosis, or neurological
disease other than stroke or the previous neurosurgery.
Participants undergo the following tests and procedures during four or more visits to the
NIH Clinical Center:
- Physical and neurological examinations and depression rating scale.
- Cognitive testing: Subjects complete written tests, sit at a computer and make
decisions about what they are shown by pressing keys, or answer questions from a test
- Behavioral training: Subjects practice performing a cognitive task that involves
looking at and making decisions about visual images that appear on a computer screen.
- Magnetic resonance imaging (MRI): Subjects undergo MRI scanning while they perform the
task they previously practiced. The MRI scanner is a metal cylinder surrounded by a
strong magnetic field. During the procedure, subjects lie still for up to 10 minutes at
a time on a table that can slide in and out of the cylinder. The entire MRI scanning
session takes about one hour. There are multiple scans which each can take up to 10
minutes. They may be asked to return for one or two additional scanning sessions.
During the behavioral training or MRI scanning, special pieces of equipment that monitor eye
movements may be used.
Some subjects may be asked to return to NIH for an additional visit to participate in a
magnetoencephalographic scan. This test uses several sensors applied to the scalp to measure
very small changes in magnetic fields. This is another way to measure brain activity.
Attention is required for most, if not all, perceptual processes. There is a converging body
of evidence from single-cell recording studies in monkeys and neuroimaging, behavioral, and
clinical studies in humans showing that the processing of attended information is enhanced
relative to the processing of unattended information.
What is the source of this attentional modulation? Because neuroimaging studies have
demonstrated that multiple cortical regions are recruited during tasks involving selective
attention, it has proven difficult thus far to determine the differential contributions of
each region. A central goal of the proposed research is to characterize the contributions of
prefrontal cortex and parietal cortex and test the hypothesis that these regions exert
top-down modulatory influences over visual processing areas. Specifically, we wish to
investigate the interaction between areas involved in attentional control and visual areas
modulated by attention.
We propose to study patients with focal lesions and normal volunteers while they perform
tasks requiring attention. Subjects will participate, first, in a series of behavioral
studies involving selective attention; the relative performance of different patient groups
and neurologically normal volunteers will be compared. Subjects will also be studied while
performing similar tasks during functional magnetic resonance imaging (fMRI). We hypothesize
that selective attention will be heavily impaired by lesions of key prefrontal (e.g.,
dorsolateral prefrontal cortex) and key parietal (e.g., superior parietal lobule) sites. We
also expect that brain imaging data will show decreased activation in visual regions
ipsilateral to the focal lesions in prefrontal and parietal cortex, thus providing evidence
that prefrontal and parietal cortex are sources of top-down modulation. Although other
research groups have compared the behavior of patients with various focal lesions or have
performed fMRI studies of visual attention in neurologically normal patients, we are unaware
of any concerted effort to perform fMRI in patients with focal lesions in order to
functionally isolate the contributions of individual cortical regions that serve as critical
nodes in the attentional network.
- INCLUSION CRITERIA:
ALL SUBJECTS -
All subjects will be volunteers and be 18 years of age or older.
Subjects with unilateral or bilateral lesions of prefrontal or parietal cortex will be
selected for participation in the behavioral and brain-imaging studies described within
Control subjects with unilateral or bilateral lesions of temporal cortex will also be
Finally, patients with amygdala lesions will also be studied to test the specific
hypothesis outlined in Experiment 4.
In order to obtain a sufficient number of focal lesion patients representative of
different brain regions, patients with different etiologies will be studied, provided the
damage is circumscribed.
The main etiologies that we will consider are stroke, lobectomy, and tumor.
We will restrict groups to include patients with the same etiology, lesion location, and
lesion volume. Lesion location will consider the two hemispheres separately.
Patients who also have non-amygdala subcortical lesions will be grouped separately from
patients with cortical-only lesions.
Our goal is to not group patients with more focal brain lesions compromising a single
region (e.g., middle frontal gyrus) with patients with more massive damage (e.g., large
extents of superior, middle, and inferior frontal gyrus).
Focal lesion patients will not be excluded on the basis of medication.
NORMAL VOLUNTEERS -
Neurologically normal, age-matched volunteers will be recruited from the local community
through normal Clinical Center channels.
The following criteria will be used to exclude patients or healthy volunteers from
participation in this study:
- Patients with language impairments that prevent them from understanding our tasks or
follow instructions will be excluded.
- Patients with a WAIS-R Full-Scale IQ of less than 75 will be excluded.
- Patients with severe cognitive dysfunction as assessed by the neuropsychological
- Subjects with moderate or severe depression as assessed by the Beck Depression
Inventory (scores greater than 18).
- Patients who cannot perform control tasks to the same level of performance as the
control subjects will be excluded.
- Subjects with contraindication to MRI scanning will be excluded from any testing
which involves the use of MRI. These contraindications include subjects with the
following devices or conditions: a) central nervous system aneurysm clips; b)
implanted neural stimulator; c) implanted cardiac pacemaker or defibrillator; d)
cochlear implant; e) ocular foreign body (e.g., metal shavings); f) insulin pump; g)
metal shrapnel or bullet; h) any implanted device that is incompatible with MRI.
- Subjects with a history of any neurological or psychiatric disorder not related to
the focal lesion (e.g., epilepsy, schizophrenia, etc.)
- Subjects with any previous head injuries not related to the focal lesion.
- Subjects with a history of drug or alcohol abuse or addiction (determined by a
- Subjects with conditions that preclude entry into the scanner (e.g., morbid obesity,
claustrophobia, etc.) will not be included in brain imaging studies.
- Female subjects of child-bearing age will be excluded from brain imaging studies if
they are pregnant or refuse to undergo a urine pregnancy test.
- Subjects with visual, auditory, motor, or language problems that would prohibit them
from being able to properly perform the visual attention tasks, to understand
instructions, indicate their responses, or to communicate with the experimenter via
an intercom system.
- Subjects who have undergone radiation treatment or chemotherapy during a one-year
period prior to the experiment.