Transcript Northwestern 2004 - Peabody Psychology

BECOMING HUMAN focuses research on brain systems,
behavior and cognition.
For example, attention deficit and
hyperactivity disorder (ADHD)
• Inattention
• Hyperactivity
• Impulsivity
Diagnosis and treatment requires
effective behavior testing.
The stop signal task probes people’s
ability to control thought and action
“Green light, red light” task.
GO
GO
STOP!
Performance in the stop signal task can be explained by a
mathematical model of a race between the process that makes
you GO and the process that makes you STOP. This model
permits determination of how long it takes to stop, the stop signal
reaction time.
Kids with ADHD have longer than normal stop signal reaction
time.
Activation
Movements
are initiated
when
certain neurons discharge a
How the brain
produces
movements
certain amount. The variability in time to start moving arises from
variability in the time taken by neurons to reach the trigger
threshold.
0.0
0.1
0.2
Time from stimulus (sec)
In the stop signal task, movements are withheld if and only if the
movement neurons are prevented from reaching the threshold.
Stop
SSRT
Activation
Go
0.0
0.1
0.2
0.3
0.4
Time from stimulus (sec)
Neurons in medial frontal lobe signal errors and success
Activation
Movement in spite of stop signal
= Error
Movement when no stop signal
= Success
-0.2
0.0
0.2
0.4
Time from movement (sec)
Error signals may originate from dopamine neuron input to
frontal lobe
A plausible link between genes, brain circuits and behavior
• Error monitoring signals are based on the activation of
dopamine neurons that comprise the brains “reward system”
Error-related negativity
• Abnormal dopamine transporter (DAT) linked to ADHD
• Explore link between DAT and impulsivity by coordinated
screening of the DAT gene and performance on the stop
signal task
5p15.3
DAT
Gene