3.7 Neuronal Synchrony

Along with iconic memory and attention, the synchronous fi ring of

neurons in areas relevant to the processing of information gathered from

a visual scene has been posited as a kind of neuronal binding mechanism.

One version of the hypothesis, put forward most forcibly by Crick & Koch

(1990, 1998, 1999, 2003), is that sets of cortical areas related to the parallel

processing of visual information are coordinated in the thalamus at a fi ring

rate of around the 40-Hertz range. Von der Malsburg (1981), Gray (1999),

Singer (1999, 2000), and Singer & Gray (1995) have put forward similar

positions that a coherent visual scene results from the synchronous fi ring

of cooperative interactions of neurons in the cortical network. The idea is

that the synchronous fi ring would bind the cells responding to different

features of the same object together for a short amount of time, so as to

produce a coherent visual perception. Neuronal synchrony has been

accepted by many as a plausible binding mechanism, since experimental

evidence has shown that relevant neuronal areas associated with the awareness

of a visual scene, even areas that are quite a distance from one another,

fi re at about the same rate (Kosslyn & Koenig, 1995; Castalo-Branco et al.,

1998; Engel, Kreiter, König, & Singer, 1991; Fries, Roelfsema, Engel, König,

& Singer, 1997; Gray, Knig, Engel, & Singer, 1989; Rodriguez, George,

Lachaux, Martinerie, Renault, & Varela, 1999; Roelfsema, Engel, König, &

Singer, 1996; Usher & Donnelly, 1998; Vaadia, Aertsen, & Nelken, 1995;

Lumer, Edelman, & Tononi, 1997; Ritz & Sejnowski, 1997). Such synchrony

could be the “holy grail” the scientist is seeking as a plausible neurological

correlate for the unifi ed phenomenal visual perception.

In one of their fi nal papers together, Crick & Koch (2003) added to the

neuronal synchrony hypothesis by putting forward the idea that cognitive

visual processing is sustained by shifting coalitions of neurons. The neurons

in a particular coalition support one another directly or indirectly and

increase the activity of their fellow members, much like what is known as

a synfi re chain. A synfi re chain, originally put forward by Abeles (1991),

refers to a signifi cant pool of neurons whose simultaneous fi ring raises the

potential of adjacent pools of neurons to allow them to fi re. Coalitions of

neurons are in a kind of competition, and attention may help in giving

one coalition a dominant position over another. When an animal attends

to a visual scene, that is, when such an animal is cognitively aware of that

scene, the neural correlation of this coherent visual scene is simply the

winning coalition. This is yet another attempt on the part of Crick & Koch

to address the binding problem, since the coalition of neurons acts as the

correlate to the bound, integrated, and coherent features of a single object

in a visual perception.

Crick & Koch’s latest idea has initial intuitive appeal because not only

do they pull together research and ideas from neuroscientists and philosophers

over the last fi fty years but they view the integrated visual scene as

resulting from a competition of coalitions of neurons. Blake & Logothetis

(2002), DiLollo, Enns, & Rensink (2000), Tononi, Srinivasan, Russell, &

Edelman (1998), and Dennett (1991) are representative of thinkers who

believe cognitive awareness results from a kind of competition, much like

Crick & Koch. Given the brain’s vast assembly of neurons receiving electrochemical

signals from other neurons and passing those on to other

neurons, Dennett (1991) thinks that cognition takes the form of something

like a pandemonium of competing bits of content, and the ones that win

the competition are the ones that are conscious.

We are now in a position to specify what is meant by visual cognition.

Visual cognition is the phenomenal representation of some object in the

animal’s visual fi eld that is the result of the integration of modular visual

information received from that object in association with iconic memory,

attention, and the synchronous fi ring of neurons in the areas of the brain

relevant to the processing of the visual percept. This defi nition is an

attempt to point in the direction of a solution to the visual binding

problem. These parts and processes may not comprise the suffi cient condition

for an overall coherently unifi ed visual percept; this is to say, there

may be some element or elements missing. However, the empirical evidence

seems to indicate that such conditions are necessary for a coherent

visual scene.

To recapitulate: visual cognition requires the integration of parallel

pieces of information concerning form, depth, motion, and so forth from

the what and the where unimodal areas (the modularity and integration

criteria); these pieces of information must be held in mind for at least 250

milliseconds (the iconic memory criterion); the pieces of information are

selected as relevant to a visual scene (the attention criterion); and neurons

relevant to the processing of such information are fi ring at relatively the

same time (the neural synchrony criterion). The end result is a coherently

bound phenomenal visual scene of which an animal is cognitively aware

when it looks at or sees something in its visual fi eld.

It is important to note again that visual cognition need not be accompanied

by consciousness. I agree with Roth (2000, p. 78) when he claims

that cognition includes perception, learning, and memory as well as limited

forms of imagination, thinking, expecting, and planning, “whether accom84 panied by consciousness or not [italics mine]” (also see Arp, 2007b, 2008b,

2008d). The above defi nition of cognition applies to all vertebrate species

in the phylum Chordata, including mammals, birds, reptiles, amphibians,

and fi sh. Roth correctly notes that consciousness comprises subjective

awareness, experience, intentionality, indexicality, and self-refl exivity.

These would be additional phenomenal states over and above visual cognition

that humans with fully functioning nervous systems have to the

fullest degree.

Several animal species engage in cognitive visual processing. They

appear to know to some degree what is going on around them as well

as being able to recall memories, make associations between objects in

their visual fi eld, and make associations between objects in their visual

fi eld and percepts stored in memory. Nevertheless, in comparison to the

human mind, there is obviously some characteristic that is missing in

the animal mind. What is it about the human mind that enables us to

solve problems to a degree such that we can fl ourish, theorize, and

dominate the earth? Humans have conscious visual experiences, as well

as other conscious phenomenal states that other species (apparently)

lack. As we will see in the next two chapters, my hypothesis of scenario

visualization will be added to the list of conscious phenomenal states,

the evolution of which has enabled humans to solve vision-related problems

creatively, construct advanced tools and other products, and dominate

the earth.

Along with iconic memory and attention, the synchronous fi ring of

neurons in areas relevant to the processing of information gathered from

a visual scene has been posited as a kind of neuronal binding mechanism.

One version of the hypothesis, put forward most forcibly by Crick & Koch

(1990, 1998, 1999, 2003), is that sets of cortical areas related to the parallel

processing of visual information are coordinated in the thalamus at a fi ring

rate of around the 40-Hertz range. Von der Malsburg (1981), Gray (1999),

Singer (1999, 2000), and Singer & Gray (1995) have put forward similar

positions that a coherent visual scene results from the synchronous fi ring

of cooperative interactions of neurons in the cortical network. The idea is

that the synchronous fi ring would bind the cells responding to different

features of the same object together for a short amount of time, so as to

produce a coherent visual perception. Neuronal synchrony has been

accepted by many as a plausible binding mechanism, since experimental

evidence has shown that relevant neuronal areas associated with the awareness

of a visual scene, even areas that are quite a distance from one another,

fi re at about the same rate (Kosslyn & Koenig, 1995; Castalo-Branco et al.,

1998; Engel, Kreiter, König, & Singer, 1991; Fries, Roelfsema, Engel, König,

& Singer, 1997; Gray, Knig, Engel, & Singer, 1989; Rodriguez, George,

Lachaux, Martinerie, Renault, & Varela, 1999; Roelfsema, Engel, König, &

Singer, 1996; Usher & Donnelly, 1998; Vaadia, Aertsen, & Nelken, 1995;

Lumer, Edelman, & Tononi, 1997; Ritz & Sejnowski, 1997). Such synchrony

could be the “holy grail” the scientist is seeking as a plausible neurological

correlate for the unifi ed phenomenal visual perception.

In one of their fi nal papers together, Crick & Koch (2003) added to the

neuronal synchrony hypothesis by putting forward the idea that cognitive

visual processing is sustained by shifting coalitions of neurons. The neurons

in a particular coalition support one another directly or indirectly and

increase the activity of their fellow members, much like what is known as

a synfi re chain. A synfi re chain, originally put forward by Abeles (1991),

refers to a signifi cant pool of neurons whose simultaneous fi ring raises the

potential of adjacent pools of neurons to allow them to fi re. Coalitions of

neurons are in a kind of competition, and attention may help in giving

one coalition a dominant position over another. When an animal attends

to a visual scene, that is, when such an animal is cognitively aware of that

scene, the neural correlation of this coherent visual scene is simply the

winning coalition. This is yet another attempt on the part of Crick & Koch

to address the binding problem, since the coalition of neurons acts as the

correlate to the bound, integrated, and coherent features of a single object

in a visual perception.

Crick & Koch’s latest idea has initial intuitive appeal because not only

do they pull together research and ideas from neuroscientists and philosophers

over the last fi fty years but they view the integrated visual scene as

resulting from a competition of coalitions of neurons. Blake & Logothetis

(2002), DiLollo, Enns, & Rensink (2000), Tononi, Srinivasan, Russell, &

Edelman (1998), and Dennett (1991) are representative of thinkers who

believe cognitive awareness results from a kind of competition, much like

Crick & Koch. Given the brain’s vast assembly of neurons receiving electrochemical

signals from other neurons and passing those on to other

neurons, Dennett (1991) thinks that cognition takes the form of something

like a pandemonium of competing bits of content, and the ones that win

the competition are the ones that are conscious.

We are now in a position to specify what is meant by visual cognition.

Visual cognition is the phenomenal representation of some object in the

animal’s visual fi eld that is the result of the integration of modular visual

information received from that object in association with iconic memory,

attention, and the synchronous fi ring of neurons in the areas of the brain

relevant to the processing of the visual percept. This defi nition is an

attempt to point in the direction of a solution to the visual binding

problem. These parts and processes may not comprise the suffi cient condition

for an overall coherently unifi ed visual percept; this is to say, there

may be some element or elements missing. However, the empirical evidence

seems to indicate that such conditions are necessary for a coherent

visual scene.

To recapitulate: visual cognition requires the integration of parallel

pieces of information concerning form, depth, motion, and so forth from

the what and the where unimodal areas (the modularity and integration

criteria); these pieces of information must be held in mind for at least 250

milliseconds (the iconic memory criterion); the pieces of information are

selected as relevant to a visual scene (the attention criterion); and neurons

relevant to the processing of such information are fi ring at relatively the

same time (the neural synchrony criterion). The end result is a coherently

bound phenomenal visual scene of which an animal is cognitively aware

when it looks at or sees something in its visual fi eld.

It is important to note again that visual cognition need not be accompanied

by consciousness. I agree with Roth (2000, p. 78) when he claims

that cognition includes perception, learning, and memory as well as limited

forms of imagination, thinking, expecting, and planning, “whether accom84 panied by consciousness or not [italics mine]” (also see Arp, 2007b, 2008b,

2008d). The above defi nition of cognition applies to all vertebrate species

in the phylum Chordata, including mammals, birds, reptiles, amphibians,

and fi sh. Roth correctly notes that consciousness comprises subjective

awareness, experience, intentionality, indexicality, and self-refl exivity.

These would be additional phenomenal states over and above visual cognition

that humans with fully functioning nervous systems have to the

fullest degree.

Several animal species engage in cognitive visual processing. They

appear to know to some degree what is going on around them as well

as being able to recall memories, make associations between objects in

their visual fi eld, and make associations between objects in their visual

fi eld and percepts stored in memory. Nevertheless, in comparison to the

human mind, there is obviously some characteristic that is missing in

the animal mind. What is it about the human mind that enables us to

solve problems to a degree such that we can fl ourish, theorize, and

dominate the earth? Humans have conscious visual experiences, as well

as other conscious phenomenal states that other species (apparently)

lack. As we will see in the next two chapters, my hypothesis of scenario

visualization will be added to the list of conscious phenomenal states,

the evolution of which has enabled humans to solve vision-related problems

creatively, construct advanced tools and other products, and dominate

the earth.