Role of the Brain in Processing Visually Presented Objects
Condition: Healthy; Motor Skills
Study type: Observational

Summary: 
      This study will examine the parts of the brain that use visual information to perform
      movements. Patients with certain brain lesions tend to have difficulty in processing visually
      presented objects. This study will look at the brain mechanisms underlying the visuo-motor
      integration.

      Healthy normal volunteers between 20 and 60 years of age are eligible for this study. People
      who have had a severe head injury with loss of consciousness or any other mental or
      neurological disorder diagnosed by a doctor may not participate. Candidates will be screened
      with a medical history, a physical examination focusing on finger movements, and a
      questionnaire.

      Participants' brain activity will be recorded using two techniques -
      magnetoencephalography(MEG) and magnetic resonance imaging (MRI) - while they watch pictures
      of various objects flashed on a screen. MEG is a procedure to record magnetic field changes
      produced by brain activity. During the recording, the subject sits comfortably in an armchair
      in a dimly lit room and watches pictures presented on a screen. About 50 pictures are shown
      per session. There are about five sessions, separated by 3-minute breaks. Functional MRI
      involves taking pictures of the brain using MRI while the subject performs a task. MRI uses a
      strong magnetic field and radio waves to obtain images of body organs and tissues. The MRI
      scanner is a metal cylinder surrounded by a magnetic field. The subject lies still on a table
      that can slide in and out of the scanner. During the scan, he or she looks at pictures in six
      test blocks of 1 minute each, with 30-second breaks between blocks.
    

Detailed description: 
      Objectives: Patients with frontal lobe lesions tend to grasp visually presented objects
      automatically and forcefully (forced grasping). Grasping of a milder form is seen in infants
      and the aged population. These facts suggest the presence of an inherent mechanism for
      suppressing the automatic tendency toward grasping in the healthy adult brain. Previous
      studies suggest that the parieto-frontal network, especially the lateral premotor cortex,
      play a role in the cognition of graspable objects and execution of reaching/grasping.
      Although the task of reaching/grasping in human beings has been studied mainly by
      neuroimaging techniques, its cognitive and executive aspects have not been clearly
      distinguished. Therefore, this project aims to elucidate the mechanisms underlying 'automatic
      grasping' in humans, focusing on the perceptive/cognitive aspect of the reaching/grasping
      movements.

      Study population and design: Pictures of graspable objects and non-graspable objects are
      visually presented to 45 healthy adult volunteers. Since this study aims to clarify the
      mechanism of the human brain for automatically recognizing graspable objects, part of this
      study will require no response task. Additionally, in order to assess how the automatic
      functions compare to overt mechanisms, an extra testing session will explore making overt
      judgments of the pictures.

      Outcome measures: The brain activations are investigated by event-related magnetic fields,
      which have high temporal resolution, and by event-related functional magnetic resonance
      imaging (fMRI), which has relatively high spatial resolution. It is expected that the lateral
      premotor cortex, in addition to the parietal cortex, is activated by the visual presentation
      of graspable objects at a shorter latency, and more strongly, as compared with non-graspable
      objects, even without any actual motor tasks to follow. Additionally, overt grasping of
      graspable objects will involve similar areas.
    

Keywords: Praxis; Grasping; Premotor Cortex; Visuo-Motor Integration; Motor Imagination