- seCtIon tHRee: BoDY AnD WoRLD
This is found bilaterally in frontal and parietal areas and mediates purposeful,
voluntary, or high-level attention. It includes response systems in the prefrontal
cortex and anterior cingulate gyrus, as well as orientating systems in the posterior
intraparietal sulcus and frontal eye fields. (Note that these systems, in cingulate
cortex and frontal areas, are distinct from the dorsal and ventral streams in the
visual system, which originate in primary visual cortex in the occipital lobe at the
back of the brain and run forwards to the parietal lobe and down into the tempo-
ral lobe respectively.)
Flexible control of attention needs dynamic collaboration of both the ventral and
dorsal attention systems to balance ‘top-down’ goals with ‘bottom-up’ sensory
inputs (Vossel, Geng, and Fink, 2014), perhaps within the wider context of feed-
back-driven probabilistic inferencing about the world (Ransom, Fazelpour, and
Mole, 2017). And the categories themselves also aren’t simple: within ‘top-down’
attentional selection, current goals may lose out to reward associations based on
past selection history, for example (Awh, Belopolsky, and Theeuwes, 2012). Neat
opposites are easy and often dangerous tools of thought (Anderson, 2011, pro-
vides a list of twelve pairs for attention alone). But fMRI studies do show that the
basic functional organisation of the two systems can be seen even when there are
no external demands (Fox et al., 2006).
An important example of involuntary attention is the bottom-up control of eye
movements. Our eyes constantly jump around from one fixation point to another.
These movements are called saccades and happen several times a second,
whether we are aware of them or not. We can also control saccadic eye move-
ments voluntarily and this involves primarily cells in the superior colliculus. If a
bright, salient, or moving object is detected in the periphery, the eyes quickly
turn to bring that part of the visual world onto the fovea. This must be done very
fast to be useful to a moving, acting animal and, not surprisingly, much of the
control is coordinated by parts of the dorsal visual stream, in particular the pos-
terior parietal cortex.
In ‘smooth pursuit’, the eyes can track a moving object, keeping its image on
roughly the same part of the fovea. This kind of eye movement is hard to make
without an actual moving target and is affected by drug use and by conditions
such as schizophrenia, autism, and post-traumatic stress. Oddly, it can continue
without conscious awareness, as was shown in experiments with a man who was
cortically blind; that is, he was blind because of damage to his visual cortex, while
his eyes and other parts of the visual system remained intact. He could not con-
sciously see movement at all, and when surrounded with a large moving stripe
display he denied having any visual experience of motion. Yet his eyes behaved
relatively normally in tracking the moving stripes, making slow pursuit move-
ments followed by rapid flicks to catch up (Milner and Goodale, 1995, p. 84). This
showed that although movement may be necessary for accurate pursuit, aware-
ness of the movement is not.
Nonetheless, even with actions as apparently involuntary as smooth pursuit, the
story is complicated. If you know which way a target will move, or know when
the motion will begin, you can initiate smooth pursuit before any movement
happens. You can keep it going if the moving target is temporarily hidden by
another object, and if you move your hand in the dark, the proprioceptive motion
signal replaces the visual signal. So even with something as apparently simple as
