Thinking is hard work. One can't have burdens and ideas at the same time. {Remy de Courmant}
"This type of [wandering] thought can be fanciful and it can be problematic and distracting,
but usually it's quite practical, for example, most people spend the time thinking about what they need to do in the impending future," said Mason.
When deciding how best to encourage daydreaming in order to study it,
the researchers recognised that our minds often wander while we are engaged in familiar tasks,
such as making a tuna fish sandwich, because we don't need to concentrate on it.
They trained study subjects to become proficient on certain tasks
so that their minds would be able to wander when they performed them,
but would have to concentrate when given something new.
The team used functional magnetic resonance imaging (fMRI)
to learn what parts of their brains were active during both goal-oriented thought and daydreaming.
In the fMRI images, the seat of daydreams appeared to be the 'default network'
a region of the brain that remains active when we rest or are not engaged in a focussed task,
but switches off 'deactivates the defaukt activities, when we need to concentrate.
The default network is a collection of regions from the medial frontal and medial parietal regions of the brain.
The frontal lobes are involved in functions including
impulse control,
judgment,
language,
memory,
motor function,
problem solving, sexual behavior,
socialisation and spontaneity.
The parietal lobe plays an important part in processing sensory information.
Previous studies have shown that brain damage to parts the default network
is associated with a "mental emptiness"
and an absence of spontaneous speech and thought.
According to Mason, the most important question is why our brains evolved to wander at all.
His team suggests that perhaps it keeps our brains aroused during mundane tasks,
or simply that our brains may wander because they can.
"In a sense these thoughts reflect an amazing capacity on our part to multi-task," said Mason.
"It is as if we have a sense of how much [attention] we have 'left over'
and allocate these resources to working out some problem
or anticipating what we have to do in the near future." ... the crossword work ?
When the brain is idling it is described as being in the default mental stage. [ DMN ]
Whatever is going on then is 'deactivated' when the brain does something.
It can be 'wandering - daydreaming, or 'fantasy in pre and post sleep state',
or 'selfreferent directed thinking', or a consideration about something outside
Those who study these states with brain scanning have not yet settled in their vocabulary.
Currently there may be more than one 'default stage' both task negative and task positive
' According to this account the reciprocal relationship between the
task-positive component and DMN
has been described as low
frequency toggling between a task-independent, self-referential and
introspective state
and an extrospective state that ensures the
individual is alert and attentive to unexpected or novel environmental
events'
Is what is happening, to sustain schizophrenia, an activity in the 'default' brain state ?
There is more widsr spread brain activity in th default stage of sufferers
Or better, perhaps there is difficulty in picking up on a 'real world' contact, during this resting phase, or after 'daydreaming?
Many flounder in fitting in again, connecting to an activity that they can recall to their attention.
That is why they are helped by the presence of a daily routine with which they can rejoin and fix their attention.
A daily routine and a regular, accessible, weekly programme
of engagement in anchoring activities is necessary where there are lingering difficulties from their illness.
Psychiatrist fail to insist this is a health NEED in aftercare
Default brain state
When we engage in almost any goal-directed behaviour of a
non-self-referential nature,
certain areas of the brain
decrease their activity when compared with a quiet resting
state (e.g., awake with eyes closed).
The consistency with which
certain areas of the brain do so,
regardless of the nature of the
goal-directed task, led to the notion of an organized default
mode of brain function
in which some regions are most active
when we are in a resting state.
The areas of the brain most
consistently displaying such behaviour regardless of task have
come to be known as the Default Mode Network (DMN)
which consists of areas in dorsal and ventral medial pre-frontal
cortices, medial and lateral parietal cortex, and parts of the
medial and lateral temporal cortices.
Recently summarized data indicate that the DMN is
involved in the evaluation of potentially survival-salient information
from the body and the world perspective,
taking a view of the
desires, beliefs, and intentions of others
and in remembering the
past as well as planning the future
All of these putative functions are self-referential in nature.
Reduction of activity in
the DMN during effort-ful cognitive processing can be
interpreted
as reflecting the need to attenuate the brain's
self-referential activity
as a means of more effectively focusing
on a task.
A failure to do so might well lead to interference in task performance from internal emotional states ( as say, seen in patients with depression).
E-mail reaction is welcome ,,, click on
A baseline or control state is fundamental to the understanding of most complex systems.
Defining a baseline state in the human brain, arguably our most complex system, poses a particular challenge.
Many suspected that left unconstrained, its activity will vary unpredictably.
Despite this prediction we can identify a baseline state of the normal adult human brain in terms of the brain oxygen extraction fraction or OEF.
The OEF is defined as the ratio of oxygen used by the brain/ to oxygen delivered by flowing blood
and is remarkably uniform in the awake but resting state (e.g., lying quietly with eyes closed).
The default mode network, a distributed network that is active when the brain is resting and that powers down during other focused mental tasks.
Local deviations in the OEF represent the physiological basis of signals of changes in neuronal activity
obtained with functional MRI during a wide variety of human behaviors.
We used quantitative metabolic and circulatory measurements from positron-emission tomography to obtain the OEF regionally throughout the brain.
Areas of activation were conspicuous by their absence.
All significant deviations from the mean hemisphere OEF were increases,
signifying deactivations [ deactivation means less oxygen extracted locally and therefore a higher ratio - brain activity/ none , and resided almost exclusively in the visual system.
Defining the baseline state of an area in this manner attaches meaning
to a group of areas that consistently exhibit decreases [ therefore activity ] from this baseline,
during a wide variety of goal-directed behaviors monitored with positron-emission tomography and functional MRI.
These decreases suggest the existence of an organized, baseline default mode of brain function that is suspended during specific goal-directed behaviors. [ So what does the brain return to when returng from idleness - the default stage - from default to some direction of emgagement with outside 'the brain' .
In ordinary daily life one returns to some part of a routine. The return is to whatever is the current part of a daily routine, then to be 'scanned' for updating, the requirements suggested by the current situation in the routine. The results indicate that the default network is hyperactive and hyperconnected in people with schizophrenia, and could be contributing to their symptoms. Instead of responding to the outside world, the brain starts to contemplate its internal landscape. background materaial to thought disorder Attenuation of DMN activity has
been described as task non-specific, ' According to this account the reciprocal relationship between the
task-positive component and DMN has been described as low
frequency toggling between a task-independent, self-referential and
introspective state and an extrospective state that ensures the
individual is alert and attentive to unexpected or novel environmental
events' Brain activity in the resting state incorporates both task-negative
and task-positive components. A second network also characterised
by spontaneous lowfrequency activity has been identified as
a task-positive network. The high degree of temporal anticorrelation
between the DMN and task-positive network, is
thought to reflect a low frequency toggling between their
associated psychological functions of introspective and selfreferential
thought, and extrospective attentional orienting,
respectively; allowing an individual to remain alert to unexpected
environmental events. Indeed, the close temporal linkage and
rivalry between associated functions is a potential argument for
considering the DMN and task-positive component as part of a
single network. Spontaneous low frequency activity in the task-negative component
of the default-mode network which is routinely attenuated
during goal directed tasks, The
default-mode interference hypothesis also highlights the importance
of efficacious transition from rest to task. Four influential
components which moderate such a transition are described:
affinity to the default-mode, The notion of wandering minds provides another possible
theory of attentional lapses during task performance, In a group of schizophrenic patients, Zhou et al. (2007) reported
significantly increased resting state connectivity in the task-positive
network and DMN in the patient group, The authors
argue that the increased anti-correlations reflect increased
antagonism and excessive competition between the networks, More interestingly,
reduced anti-correlations were evident between the right
dorsal premotor cortex and the PCC and bilateral parietal region of
the DMN Finally, in schizophrenia, increased connectivity between the
DMN and other resting state networks In contrast, some research
has reported widespread decreased regional homogeneity in the
DMN in schizophrenic patient groups (Liu et al., 2006).
Altered patterns of functional connectivity within the DMN and Increased connectivity within the
DMN and task-positive network suggests paranoid schizophrenic people
demonstrate increased sensitivity to both the external environment
and self-referential or introspective thought.
In an n-back working memory task, Pomarol-Clotet et al. (2008) ICA analysis has also revealed differences in both
spatial and temporal connectivity of the DMN during an auditory
oddball task (Garrity et al., 2007).
Moreover, a greater section of parahippocampal gyrus was
included in the DMN of patients, and while low-frequency
oscillations (0.03 Hz) in the DMN were evident for controls,
patients showed significantly higher frequency oscillations (0.08–
0.24 Hz). Finally, greater deactivation in the MFG, precuneus, and
the left MTG were correlated with positive symptoms of
schizophrenia (Garrity et al., 2007).
Consistent with the task-related findings of Garrity et al. (2007),
disconnectivity of the low-frequency oscillatory (<0.1 Hz) activity
in the PCC, medial prefrontal, lateral parietal and cerebellar regions
during rest
Although in contrast, a recent finding of increased connectivity
between the DMN and other resting state networks using spatial
ICA, has been hypothesised to reflect distraction and hallucinatory
experiences of schizophrenic patients (Jafri et al., 2008). The
relationship between the apparent self-monitoring function of
regions within the DMN and schizophrenia provide impetus for
future research. However, the disparity in methodologies and
findings highlight the need for methodological consistency if we
are to properly understand the association between functional
connectivity in the DMN and underlying mechanisms that give rise
to the symptomology of schizophrenia (Williamson, 2007).
In summary, greater connectivity in the DMN and task-positive
network in schizophrenic patients may reflect ‘over-zealous’
attentional orientation to introspective and extrospective thought,
Increased deactivation of specific DMN regions including
MFG and precuneus :
The network is also affected in healthy, first-degree relatives of subjects, suggesting that the changes could be part of the genetic risk for the disease.
The idea is that there are widespread deficiencies in cortical processing in schizophrenia, and suggests that these deficiencies affect a brain network thought to be responsible for self-awareness and internal reference.
This is when new and creative connections are made between seemingly unrelated ideas.
[ and maybe where sufferers from schizophrneia have trouble in distinguishing the flight of associations in this state with external causes ??? I don't mind being muddled in this speculation - nobody else knows any better - do they ? }.
the extent to which goaldirected
activity influences this attenuation is dependent
at least in
part,
on cognitive load and task requirements involving functions
subserved by regions within the DMN.
The DMN has been described as a
task-negative network given the apparent antagonism between its
activation and task performance.
This network includes the dorsolateral
prefrontal cortex (DLPFC), inferior parietal cortex (IPC) and
supplementary motor area (SMA) and appears to be associated
with task-related patterns of increased alertness, and has also been
related to response preparation and selection (Fox et al., 2005,
2006a; Fransson, 2005, 2006; Sonuga-Barke and Castellanos, 2007).
,
Interestingly, the task-positive network and the DMN are temporally
anti-correlated, such that task-specific activation of the task-positive
network is affiliated with attenuation of the DMN.
can under certain circumstances (e.g.
suboptimal motivational states or in individuals with attention
disorders)
persist into or re-emerge during periods of task-related
active processing
to such an extent that it competes with taskspecific
neural processing and creates the context
for periodic
attentional intrusions/lapses and cyclical deficits in performance;
the temporal signatures of task-negative fluctuations being
mirrored in patterns of attention and performance
affinity to the goal-directed state
or
intrinsic motivation, extrinsic motivation
and the accessibility and
degree of cognitive effort (see Sonuga-Barke and Castellanos,
and it is
conceivable that generalised deficits in attention and cognitive
control
may well coincide with an increased incidence of stimulus/independent
thought or mind wandering and the intrusion of
increased activity in the DMN.
alongside
significantly increased anti-correlations between the networks.
These results were more specifically associated with bilateral/dorsal MPFC, inferior temporal gyrus, and lateral parietal region in
the DMN;
and right dorsal lateral PFC and bilateral insula and
orbital frontal gyrus in the task-positive network.
and most likely contribute to the over-mentalising and deficit in
attentional control symptomatic of schizophrenia.
and suggest that the right dorsal premotor cortex may be
instructive in mediating the anti-correlation between the DMN
and task-positive networks
suggests greater dependence
on other resting state networks, most likely associated with
increased distraction due to hallucinations and delusional
experiences (Jafri et al., 2008).
Moreover, increased connectivity
within the DMN and task-positive network in schizophrenic
patients at rest
implies that these individuals are susceptible to
over-mentalising and excessive alertness to the external environment,
respectively (Zhou et al., 2007).
The strength of
the anti-correlation between these two networks also indicates
that these processes are in excessive competition for this patient
group (Zhou et al., 2007).
report reduced activation of the DLPFC in patients with schizophrenia
to be a function of impaired task performance.
In contrast,
a reduced deactivation of the DMN in the medial frontal area was
not found to be dependent on task performance (Pomarol-Clotet
et al., 2008).
In this study, and in contrast to
Pomarol-Clotet et al. (2008), schizophrenic patients showed
greater deactivation of the DMN in the frontal gyrus,
and decreased
activation of the ACC relative to controls, potentially related to
attentional deficits observed in schizophrenia (Garrity et al., 2007).
has also been observed in another two studies
examining this clinical group during rest (Bluhm et al., 2007)
and during a similar auditory oddball task (Calhoun et al., 2008).
while the increased anti-correlation between these two networks
suggests excessive rivalry or antagonism between the neural
processing and associated psychological functions of these networks.
was associated with the positive symptoms of
schizophrenia, while reduced deactivation of ACC was suggested to
be associated with reduced attentional control.