1. Beatrice Gomes
Dr. Brasier
Controversies in Neuroscience
Multiplicative Model of Attention
One of the major controversies in the field of neuroscience is the contrast gain
versus response gain models of attention. A number of studies have been conducted in
order to identify the model that best explains how attention operates within the human
brain at the neuronal level. By observing the numerous studies made on attention, one can
conclude that attention follows the multiplicative, or response gain, model. Research
studies conducted on the visual cortex and the superior colliculus support the
multiplicative theory of attention.
John H.R. Maunsell published a paper detailing the study he conducted on the V4
and V1 brain areas in rhesus monkeys in order to gain insight into the attentional model of
the brain. These are visual regions in the occipital lobe that processes visual information
and object recognition. Neurons in the V4 area of the brain are sensitive to line orientation,
so the study utilized lines as the targets. The study aimed to research the responses of
neurons in the extrastriate visual cortex when the subject, in this case the rhesus monkey,
had to attend to a target object. The experiment was conducted by training monkeys to
stare at a central spot while stimuli were presented on both sides of the central spot; if the

2. monkeys paid attention to one of the flashing stimuli on either side of the central spot, they
were given juice by the researchers (Maunsell 431). The experiment concluded that the
evoked responses in the monkeys were consistent with a multiplicative scaling due to the
percentage increases recorded in neuronal responses to attention or the lack thereof
(Maunsell 437). In other words, attention was found to follow the multiplicative, or
response gain, model.
Michele A. Basso led a study on attention in the context of visual responses. The
study looked at neurons in the superior colliculus of monkeys, a structure that resides on
the brainstem. The neurons were classified as buildup, visual motor, visual tonic, and
visual phasic according to their activity during the delay intervals (Basso 4562). The
monkeys were provided with luminance gratings in order to measure spatial attention
(Basso 4561). The purpose of the experiment was to observe the phenomenon of saccades,
or rapid eye movements between fixed targets; in the context of the experiment, this meant
measuring the monkeys’ visual focusing on the scattered luminance gratings (Basso 4561).
The electrophysiological recordings of neuronal activity and eye movements were gathered
by implanting cylinders and eye movement measuring loops in two rhesus monkeys (Basso
4562). The experimenters varied the contrast of the stimuli to determine the monkeys’
responses to color cues. The researchers collected the information on the monkeys’
superior colliculus neuronal activity and their saccades following the appearance of the
luminance gratings around the central spot and concluded that luminance contrast
modulates superior colliculus neuronal activity (Basso 4564). The researchers also

3. concluded that response depends on the sensitivity of the neuron and the strength of the
stimuli, in this case being the luminance of the targets. The graphs of the data collected
from the monkeys follow the response gain, or multiplicative model of attention.
However, John H. Reynolds arrived at a different conclusion when researching
attention. Reynolds chose to look at the neurons in the V4 area of the visual cortex, which
respond to position and orientation (Reynolds 703). The experiment involved flashing
lights on the screen for 250 millisecond intervals of time; the non­target objects were thin,
rectangular patches of sinusoidal grating and the target objects were square patches of
grating because of their lack of orientation (Reynolds 712). The experiment involved
giving monkeys a simple attentional task, staring at a small spot in the center of a screen
and pressing a bar when the target stimulus appeared, with the prospect of juice rewards
for ignoring foil targets, or distractors (Reynolds 704). If the monkeys responded to the foil
targets, they were not given the juice reward in order to train them to recognize the rotated
targets. Reynolds found that the neuronal responses to low contrast (5%) and high contrast
(80%) were similar (Reynolds 706). The results led Reynolds to conclude that, “Attention
causes an increase...in neurons’ sensitivity but without a substantial increase in the
response to high­contrast stimuli” (Reynolds 707). In conclusion, Reynolds’s experiment
provided some evidence for the additive, or contrast gain theory of attention.
The theories of attention and neuronal responses clash, but one prevails: the
multiplicative, or response gain theory. By looking at the studies conducted on neuronal
firing in both the visual cortex and the superior colliculus, one can conclude that attention

4. within the brain follows the model given in response gain theory due to the fact that
varying the parameter of contrast has a multiplicative effect on the firing of neurons
dedicated to attending to stimuli.

5. Works Cited
Maunsell, John H.R., and Carrie J. McAdams. "Effects of Attention on Orientation­Tuning
Functions of Single Neurons in Macaque Cortical Area V4." ​The Journal of
Neuroscience​ 19.1 (1999): 431­41. Web.
Basso, Michele A., and Xiaobing Li. "Preparing to Move Increases the Sensitivity of
Superior Colliculus Neurons." ​The Journal of Neuroscience​ 28.17 (2008): 4561­577.
23 Apr. 2008. Web.
Reynolds, John H., Tatiana Pasternak, and Robert Desimone. "Attention Increases
Sensitivity of V4 Neurons." ​Neuron​ 26 (2000): 703­14. Web.