Two open access studies, differently formulated, agree that three areas of the brain concerned with memory capacity show up as being needed to work together to be able to complete intentions.The hippocampus is part of this,.
Study 1.
Kond et al Kondo et al. BMC Neuroscience 2010, 11:147
This paper studied the distribution of white matter damage after brain trauma.
The areas of focal damage can be discovered and site deficiencies then correlated to the results of the sequence of brain changes in Prospective Memory [ PM ] tasks.
PM involves remembering to carry out intended actions at appropriate points in the future
Even minimal reflection prompts the realization
that the texture of our daily existence is inextricably
bound to PM tasks.
Everyday life cannot go on without it.
remembering to load one's
bicycle into the car for a ride after work.
Finding and keeping the background to enable an extende conversation
Everyday memory performance was evaluated using standardized
profile scores of the PM failure
was assessed using the following three sub-tests of
Rivermead Behavior Memory Test. Results In previous PET studies, activation
of the left parahippocampal gyrus has been observed
during the 'loading preparation' of subjects doing experimental PM tasks, Lesions in the left anterior cingulate causing PM
failure were associated with failure of recall of the intention
and intended action [ keeping the intention in mind ]. These findings suggested
that PM failure might reflect operation of the
supporting retrospective components of PM,
In the Left inferior parietal
lobe, activation
this area was observed on loading of the Wisconsin
Card Sorting Test and Trail Making Test, or inhibiting other activities at the critical time
for performance of the intended action Summary Using lesion-symptom analysis, we demonstrated that
lesions These structures may thus be included in
the neuronal circuit of PM. Study 2. 2. This study had the brains of subjects being subject to imaging , and their eye movements recorded, whilst pursuing a journey in a Google map type display in 'Virtual Reality'. The subjects also commented afterwards on what they were thinking as they watched the rcorded stages of the 'journey'. It refers
to the ability to remember to perform previously planned actions in the future, such as doing errands . PM has traditionally been described
as consisting of successive phases or components such as 1. 2. 3. 4. 5. 6. (2) (3) (4) (5) Note that ''Roaming'' replaces Intention Maintenance before TD (phase 1) Animation occurred when the subject pressed the button to
indicate the execution of the task and displayed the action. These time points
were confirmed by the subjects in their verbal reports Action, corresponding to the retrieval of the
retrospective component of PM
Finally, the switching phase was defined as the time-point when one
task was finished The two intention maintenance phases
were contrasted with periods when the participants did not have
any active intention in mind (''roaming''), which notably occurred
instead of ''intention maintenance before TD''
A model, was proposed for virtual PM shaped
as a multi-phase iterative loop,
Result, the activation of an attentional network primarily shown
in experiments on attention: the visual top-down attentional
network (or dorsal system) in which the FEF and the superior
parietal cortex constitute key regions (
conjunction analysis).
Indeed, when comparing the two maintenance periods, it
appeared that a perceptual ( visual) system was more engaged
before the target of interest was found, First, this parietal region
could have a role in bottom-up AtoM [ Attention to Memory ]. Second,
it has been claimed that this region would subserve the episodic
buffer sub-system of working memory, Third, this region may play the role of a mnemonic
accumulator,
Despite the fact that the action phase was reduced to a single button press
The hippocampus has been strongly related to spatial
memory, in humans and non-humans. .
VR studies in epileptic patients along with cellular recordings
showed hippocampal neuronal firing for specific places We,
too, observed hippocampal activity when subjects were located at
specific places,
The assumption that episodic memory was involved at
Action
In the neuro-imaging literature, In the current task
(and most real-world PM tasks), switching is one phase of PM that
makes possible the deactivation of a just-performed task The Temporo Parietal Junction [ TPJ ] and superior parietal cortex were also activated at
switching
The combination of virtual reality fMRI, eye-tracking, and postscanning
verbal assessment As for naturalistic studies of retrospective
episodic memory (autobiographical memory), spatial navigation,
and future thinking, back to studies of working memory and the hippocampus
First, the 'belonging sub-test' required the participants
to ask for a personal belonging, which was taken
from them at the beginning of the assessment, when the
examiner indicated that the assessment had finished.
Participants were also required to remember where the
item was concealed.
The final measure required the participants
to deliver a message at a designated place while
completing the RBMT route test. This sub-test had
immediate and delayed (30 minutes later)
Using lesion-symptom analysis,
[ which correlates areas of damaged axons with the stages of Prospective memory tests ],
we demonstrated that
lesions in the left parahippocampal gyrus, left inferior
parietal lobe, and/or left anterior cingulate resulted in
PM failure.
Activation
of this region was therefore thought to play a role in recognition
of cues triggering the performance of intended actions
as well as
those related more specifically to maintenance of an
intention.
suggesting
that neuronal activity in the left inferior parietal area reflects the cognitive
process of 'set shifting' , consisted mainly of subcortical white matter
with partial involvement of cerebral cortex. ....
... Set shifting' is believed to
participate in PM by monitoring the environment
for cues to re-instantiate any intention while performing
other tasks
( i.e. the second phase of the PM
process )
( i.e. the fourth
phase of the PM process ).
in the left parahippocampal gyrus,
left inferior
parietal lobe,
and/or left anterior cingulate resulted in
PM failure.
Kalpouzas et al :- summary and extracts
PM needs working multiple
processes, such as attention to what is going on and to what is intended, exercising 'will do', and being able to look back to a holding memory to recall.
formation of an intention –
retention over an interval –[ hanging on to what is to be done ]
recognition of a retrieval
cue [ what is it I am supposed to be doing ] –
remembering that something has to be done in a future time and place
Remembering in particular what that is
Doing it
This study:-
5 stages:-
(1) Intention maintenance before target detection (TD): the subject is actively looking for a hot-dog
stand,
Target Detection [ TD ]: the subject detects the stand to go to ( a yellow dot represents gaze fixation via the eye-tracking system ,
Intention maintenance after TD:
the subject is heading towards the stand with the intention of buying a hot-dog,
Action: the subject presses the button to indicate that he or she
buys a hot-dog,
Switching: the task is terminated and the subject activates another intention in mind; {
''End'' was used instead of switching at the
end of the last task of a route performed by the subject.}
in cases where no
intention was activated by the subject
but was triggered by the perception of the target.
TD was defined as the time-point when
the gaze was positioned on the target for the first time.
as
constituting the times when they did recognize the targets as being
prospective cues.
(i.e., what has to be done in
relation to the target),
was defined as the time
when the subject
pressed a button to indicate that he or she was performing the task.
and the subject had to switch focus from the just
executed task and activate a new intention.
as
well as the ''animation'' phase after the action was done.
consisting of two intention
maintenance phases,
TD, action and switching , with these
phases involving an interactive engagement of perceptual,
attentional and mnemonic networks
as well as updating as
developed below.
As recently suggested, this network would
also be engaged when attention is directed towards episodic
memory retrieval (or attention to memory - AtoM ) to support
maintenance of goals in mind
. Thus, top-down attentional
mechanisms would govern PM during almost the entire task
until
the action can be realized,
while other additional neurocognitive
systems were engaged, separately during each intention maintenance
period.
and inferior parietal areas
were more activated in-between Target Detection and Action
While the differential activation of the occipital areas is
most likely linked to the search of the target ( supported by the eye
movement data ]
the involvement of the inferior
parietal cortex after TD was less expected.
The function of this
region is an ongoing matter of disagreement, and at least three
different views have been suggested
In contrast with top-down
AtoM, where internal attention is directed towards the external
world,
because attention is captured by an external cue
that matches with
the mental representation of what is to be recovered .
defined as a system able to
temporarily maintain bound episodic information in working
memory
such that it accumulates evidence until a criterion for
the decision-making of recognition is reached
A point that
has been largely neglected in this debate
is the exact location,
within the inferior parietal cortex, of the three suggested systems.
The fact that the angular gyrus and, less strongly, the intraparietal
cortex were activated in a sustained manner
between Target Detection and
Action indicates that they may serve as memory buffers and/or
accumulators rather than bottom-up AtoM.
The latter being more
likely to intervene in a transient manner.
Regarding the episodic
buffer hypothesis, a meta-analysis showed that it is partly
located in the angular gyrus.
Concerning the mnemonic
accumulator hypothesis, a review of the literature showed evidence
that the intraparietal sulcus was mainly implicated
Thus, the
episodic buffer, underpinned by the angular gyrus, would mainly
be involved during intention maintenance after Target Detection,
allowing
holding of episodic information in relation to the target until
the action can be performed.
Although the activity of the
intraparietal sulcus was revealed at a lenient [ less significant ] threshold and would
thus need further investigation,
its function of information
accumulation would fit well within this present construct of PM.
(a feature of
the task that should be improved in future experiments),
brain
areas known to be involved in episodic memory retrieval were
activated,
notably the ventrolateral prefrontal cortex and regions
of the medial temporal lobe (MTL) including the hippocampus
Cellular recordings in the
hippocampus in relation to spatial memory - while rodents are
freely moving
in natural-like environments such as mazes -
have
revealed insights into complex brain-behavior relations
but the current PM model indicates that in
humans, hippocampal activity does not only reflect spatial
information processing
but the use of such information for
episodic retrieval
Activity in the hippocampus was mainly
left-sided, which may indicate and further support the dissociation
between the left episodic hippocampus and right spatial hippocampus
is further supported by the fact that in the encoding phase,
the subjects had to visualize themselves performing the tasks,
elaborating then a representation for each action
that was likely reactivated
in the PM-VR experiment,
and more particularly at
Action.
switching (or shifting) has been
the second most present process together with intention maintenance
in non-naturalistic PM experiments
. Indeed, in such
tasks, and in contrast to the present experiment,
PM is structured
as a task to do instead of another task
(the so-called ongoing task)
and
where the subjects have to immediately inhibit the ongoing activity
in order to respond to a predefined prospective cue when it
appears,
resulting in
(1) in the absence of an intention maintenance
phase in between TD and action that is however frequent in real
life,
(2) the possible confound of target detection, execution and
switching mechanism per se,
which has made difficult the
interpretation of Brodmann Area 10 involvement in PM.
and the
activation of a new intention in mind.
Interestingly, this was the
only time point of the task where a frontopolar (BA 10) area was
detected, however at a 'lenient; threshold,
which needs to be
confirmed with other experiments
Its hypothesized
presence would nonetheless be supportive of its specific role in
''branching'' control, allowing attention shifting between tasks
indicating an updating process
as for TD
such that information that the task has been
successfully accomplished
is transmitted to the dorsal system,
updating its content and likely inducing the activation of a new
goal.
were decisive in elaborating a more
complete and realistic neuro-functional model of PM,
defined as a multi-phase iterative loop with
engagement of top-down attention throughout one PM task,
allowing maintenance of a goal in mind, and a shift between
perceptual processing (visual search) and mnemonic systems
(episodic memory, episodic buffer in working memory)
when the
target was recognized.
using a combination of methods allowed us to contribute to the understanding of
how the brain dynamically
guides PM functioning in real-life.Copyright: 2010 Kalpouzos et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited