Neurobehavioral Assessments of Cerebral Vasospasm - Animal Models of Acute Neurological Injuries: Injury and Mechanistic Assessments - page 565

provides evidence for dorsolateral PFC being involved in working
memory, attention, and task switching; ventrolateral PFC in object
categorization, rule learning, and inhibitory control; orbital PFC
in reward-based decision making; medial PFC in monitoring and
operant conditioning, especially when it entails multiple stimuli
and response options; and fi nally, frontal polar cortex in higher-
order planning and feedback monitoring; see refs. ( 206, 235-241 ).
We describe basic tasks that can be used to assess damage in each
of these general regions of PFC.

One of the most classic fi ndings in cognitive neuroscience is the
involvement of dorsolateral prefrontal cortex (especially Brodmann's
area 46) in working memory function ( 206, 241-243 ). The main
task to test working memory is the delayed-response task, typically
involving two choice alternatives. Monkeys are cued as to which of
the two choice alternatives will yield a reward, a delay is then insti-
tuted, and the monkeys are then allowed to make their choice.
The monkeys must use working memory to remember the cued
alternative. This same PFC region also appears to subserve atten-
tion; and in fact, some evidence suggests that it is more involved in
attention than in working memory, when both are pitted against
each other ( 244, 245 ). To test for attentional defi cits, the cuing
tasks described above for testing attentional defi cits due to PPC
damage can also be used. Attentional defi cits may also include the
inability to disengage attention and direct it to another location or
stimulus category. The Wisconsin Card Sorting Task has been used
to study such defi cits in humans, and analogs to this task can be
used with monkeys ( 246, 247 ).

7.8.1. Dorsolateral
Prefrontal Cortex

Evidence suggests that ventrolateral PFC is involved in several higher-
order cognitive processes, including the categorization of objects,
rule learning, and inhibitory control ( 241, 248 ). MTS task and its
variants, as described under tests of temporal lobe dysfunction above,
can be used to study object categorization ( 249 ). Rule learning and
performance can also be tested using paradigms that require mon-
keys to switch between two different rules according to instruction
cues, such as switching between MTS and NMTS ( 250 ).
Finally, inhibitory control ability can be tested with several
tasks. One of the most popular and straightforward is the stop-
signal task. In this task, subjects are required to respond as quickly
as possible once they see a go cue. The response can be a saccade to
a particular target from a fi xation point or reaching to a particular
target. On certain trials, however, a stop signal may follow the go
signal, which then requires subjects to withhold the response. As the
stop signal becomes more delayed after the go signal, cancelling
the response becomes more diffi cult, providing a sensitive measure
for how well the inhibitory control process is working ( 251, 252 ).

7.8.2. Ventrolateral
Prefrontal Cortex