The was the second week of discussion about the default mode network versus the task positive network and a few other of the 40 plus networks of brain function that we now know about. The following is a paraphrase of a handout that Paul distributed this date to clarify some of the vast information that has been discovered about these brain networks.
There is a very nice partial chapter describing what we know about these networks in a very complete tome, by Dan Levitin, entitled The Organized Mind.
Last week we learned the definition and characteristics of the default mode network, which is a connections of several vary important parts of the brain that cycles in and out on an average of 5 to 100 seconds, with an average cycle length of 20 seconds. The network that is basically our "day dreaming" network takes over with these kind of cycles whether we want it to or not. However there are ways to keep it in abeyance. One such way is to activate the task positive network which is the network that takes effect when we are consciously trying to either complete a task or also when we are doing concentrative meditation.
The various parts of the task positive network are the dorsal attention pathway and the ventral attention pathway. The dorsal attention pathway (egocentric) is over the top of the brain and bilateral in a top down fashion. The ventral attention pathway (allocentric) is located primarily underneath the brain, and tending to end up mostly in the right hemisphere (bottom up). this pathway is an alerting pathway.
James Austin says that these areas anti-correlate, but other authors don't mention this.)
In general, the ventral attention pathway is considered "bottom up", and is the first network recruited by new alerting situations, usually initiated by the salience network. Let's examine what the salience network is. The salience network is underneath the frontal lobe, and involves the right insula. It is the network that gets activated upon a significant event in the environment. . It is therefore somewhat of a traffic cop. It usually anti-correlates with the default mode network. According to Wikipedia, the salience of an item whether it is an object, a person, a light, etc, is the state or quality by which it stands out relative to its neighbors. Saliency detection is considered to be a key attentional mechanism that facilitates learning and survival by enabling organism to focus their limited perceptual and cognitive resources on the most pertinent subset of the available sensory data.
"Saliency typically arises from contrasts between items and their neighborhood, such as a red dot surrounded by white dots, a flickering message indicator of an answering machine, or a loud noise in an otherwise quiet environment. Saliency detection is often studied in the context of the visual system, but similar mechanisms operate in other sensory systems. What is salient can be influenced by training: for example, for human subjects particular letters can become salient by training."
Wikipedia article goes on the state that "when attention deployment is driven by salient stimuli, it is considered to be bottom-up, memory-free and reactive. Attention can be top-down, memory-dependent, or anticipatory mechanism, such as when looking ahead of moving objects or sideways before crossing streets. Humans and other animals have difficulty paying attention to more than one item simultaneously, so they are faced with the challenge of continuously integrating and prioritizing different bottom-up and top-down influences. "
Paul goes on in his summary handout, the dorsal attention pathway is more top down and is related to resolving conflict, initiating action. It basically selects what to pay attention to.
Another network located mostly in the frontal lobe is the executive control network. At rest this network anti-correlates with the default mode network. When awareness of daydreaming occurs, this network starts to correlate with the default mode network. The executive control network is the area where decisions are often made.
As was commented above, one way to take more control of the default mode network is to meditate. The concentration of meditation engages the task positive network. However, there are two different types of meditation which contrast and seem to strengthen either the default mode network or the task positive network. Utilizing these contrasting forms of meditation would seem to strengthen one or the other of these networks thus enhancing a balance between the two. Here is a contrast between these two types of meditation.
Receptive versus concentrative meditation.
Receptive Concentrative
more effortless and unfocused effortful, sustained
universal bare awareness deliberate one-pointed attention
Global monitoring and bottom-up voluntary, top-down processing
other referential self referential
"open pasture" "cow squeezing"
more effect on default mode network more effect on task positive network
examples: examples:
meditation on thought body scan
sky gazing lovingkindness meditation
vipassana samatha
increase strength of connections increase strength of connections
in default mode (and ? VAN) in task positive network
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