140 • CHAPTER 5 Short-Term and Working Memory
at a particular place, and this information about where the
object was remains available for as long as these neurons con-
tinue fi ring (also see Funahashi, 2006).
Research has also found neurons that are involved with
working memory in other areas of the brain, including the
primary visual cortex, which is the fi rst area of the brain to
receive visual signals (Super et al., 2001), and the temporal and
parietal areas, where visual information is transmitted from
the primary visual cortex (Jonides et al., 2005). Thus, although
the PF cortex may be the brain area that is most closely asso-
ciated with working memory, other areas are also involved.
This idea that a number of areas of the brain are involved in
working memory is another example of distributed process-
ing (see Chapter 2, page 36) that we described for perception
(Chapter 2, page 37) and attention (Chapter 4, page 107).BRAIN ACTIVATION IN HUMANS
The conclusion that many brain areas are involved in work-
ing memory has been confi rmed by research using imaging
techniques such as PET and fMRI to measure brain activity
in humans. These studies show that as a person carries out a
working memory task, activity occurs in the prefrontal cortex
(Courtney et al., 1998) and in other areas as well (Fiez, 2001;
Olesen et al., 2004). ● Figure 5.26, which summarizes the data
from many experiments, shows that in addition to the prefron-
tal cortex, other areas in the frontal lobe and also areas in
the parietal lobe and the cerebellum are involved in working
memory (Cabeza & Nyberg, 2000).
In addition to determining which areas of the brain are involved
in working memory, researchers have also been concerned with
determining how the brain is involved in the “workings” of working
memory. For example, one of the functions of the central executive
is to focus attention on items that are important for a task and to
ignore items that are not relevant to the task.
Edward Vogel and coworkers (2005) did an experiment on the
allocation of attention by measuring a component of the event-
related potential (ERP) in humans, recorded during a working mem-
ory task. (See Method: Event-Related Potential, Chapter 2, page 34.)
The response they measured was related to encoding items in work-
ing memory, so a larger ERP response indicated that more space was
used in working memory.
What makes Vogel and coworkers’ experiment interesting is that
they separated participants into two groups based on their perfor-
mance on a test of working memory. Participants in the high mem-
ory capacity group were able to hold a number of items in working
memory; participants in the low memory capacity group were able
to hold fewer items in working memory. Both groups viewed the
stimuli shown in ● Figure 5.27. They fi rst saw a cue indicating
whether to direct their attention to the red rectangles on the left side
or the red rectangles on the right side of the displays that followed.
They then saw a memory display for one-tenth of a second, followed
by a brief blank screen and then a test display. On some trials, two
red rectangles were presented on the left and right sides of the dis-
play, as shown in Figure 5.27a. On other trials, two red rectangles
and two blue rectangles (which the participants were told to ignore)
were presented (Figure 5.27b).● FIGURE 5.26 Some of the areas in the cortex that have
been shown by brain imaging research to be involved in
working memory. The colored dots represent the results of
more than 60 experiments that tested working memory for
words and numbers (red), objects (blue), spatial location
(orange), and problem solving (green). (Source: R. Cabeza & L. Nyberg,
“Imaging Cognition II: An Empirical Review of 275 PET and fMRI Studies,” Journal of
Cognitive Neuroscience, 12, 1–47, 2000.)Verbal and numbers
Objects
Spatial
Problem solving● FIGURE 5.27 Sequence for the Vogel et. al (2005)
task. The arrow in this example tells the participant to
pay attention to the left side of the memory and test
displays. The task is to indicate if the red rectangles on
the attended side are the same or diff erent in the two
displays. (a) Display with two red rectangles on each
side of the display. (b) Display with two blue rectangles
added to each side. The participant is told to ignore the
blue rectangles. (Source: Based on E. K. Vogel, A. W. McCollough, & M.
G. Machizawa, “Neural Measures Reveal Individual Differences in Controlling
Access to Working Memory,” Nature 438, 500–503, 2005.)(a)(b)++++Cue Memorydisplay Delay displayTest++++Cue Memorydisplay Delay displayTest200 ms 100 ms 900 ms 2,000 msCopyright 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.