R E C A L L I N G R O U T E S A R O U N D LO N D O N : AC T I VAT I O N O F T H E R I G H T H I P P O C A M P U S I N TA X I D R I V E R S

grassquantityAI and Robotics

Nov 15, 2013 (3 years and 6 months ago)

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MAGUIRE E.,
FRACKOWIAK

R., FRITH C. (1997)

R E C A L L I N G R O U T E S A R O U N D
L O N D O N: A C T I V AT I O N O F T H E
R I G H T H I P P O C A MP U S I N TA X I
D R I V E R S



J O U R N A L O F N E U R O S C I E N C E, 1 7, 7 1 0 3
-
7 1 1 0

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WHERE IS SPATIAL MEMORY?

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POSITRON EMISSION TOMOGRAGRAPHY (PET) SCAN

PET


positron emission tomography


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MAGUIRE ET AL (1997)

Aim:

Investigate the neural basis for spatial memory


Method:

Using PET, measure neural activity during
topographical (=space/location) semantic
(=facts/language) memory tasks

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MAGUIRE ET AL (1997)

Participants:

11

London black
-
cab taxi
drivers

Average age 45

Average experience 14.5 years




Informed written consent

Local hospital ethics committee approved the study

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PROCEDURE

Factorial design, 2 factors of interest:

Topographical and sequencing memory


Why? To distinguish
brain activity during route planning,
i.e.
places

in order

(topo. & seq.),
from
brain activity during other types of memory task


How?

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PROCEDURE

Tasks: describe…


routes (shortest legal)


T+ S+

landmarks (not in London)


T+ S
-

film plots (famous)


T
-

S+

fi l m frames (stills)


T
-

S
-

4
-
digit numbers (baseline comparison task)


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PROCEDURE

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T+

T
-

S+

Routes

Film plots

S
-

Landmarks

Film

frames

CONTROLS

repeat 4
-
digit numbers as baseline comparison task


participants blindfolded throughout


speech output digitally recorded


identical procedure for each participant

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PET SCANS

Data is gathered over 90 seconds following the radioactive injection


During each scan one item is presented (i.e. one route / plot / landmark / frame)

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RESULTS

Comparing the two factors…


memory type:

topographical vs. non
-
topographical


sequencing:

with vs. without


…with the baseline condition…


number repetition


…gives a picture of the neural systems supporting each task

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RESULTS

Simple

main effects

Routes recall:


increased activation of
the medial parietal lobe, posterior cingulate cortex, parahippocampal gyrus and
the R
hippocampus

Landmarks recall:


increased activation of
the medial parietal lobe, posterior cingulate cortex, parahippocampal gyrus,
oocipitotemporal regions but
not the R hippocampus


Film plots vs. frames, no sig. diff. in rCBF


(=Regional cerebral blood flow)

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CONCLUSIONS


o
semantic topographical memory retrieval is associated with the R hippocampus


o
‘entirely different’ brain regions are activated during
topographc

and non
-
topographic memory retrieval


o
the
role of the R hippocampus (and some specific other brain regions) in
processing
spatial layouts

over
long time
periods


o
both
topographical tasks (routes and landmarks) activated many of the same
brain
areas


o
main
difference: activation of R hippocampus in routes task, not in landmarks
task.
Route
planning (=navigation)

appears to be located
in the
R hippocampus






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W
HERE

IN

THE

BRAIN

IS

THE

HIPPOCAMPUS
?

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The hippocampus is
located in the mid
temporal lobe


The role of the
hippocampus is to
facilitate spatial
memory (navigation)


Each hemisphere of
the brain has a
hippocampus


Hippocampus means
seahorse and that’s
what its named after!!!

APPLICATION

Is this research useful?

Why? Why not? Does it matter?

Topographical disorientation after brain lesions


Humans and many animals can navigate in large
-
scale space. Many species with far smaller brains
can navigate successfully.

Navigation is a phylogenically old ability


located in
the ‘primitive’ hippocampus, not in frontal cerebral
regions.

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EVALUATION

Small sample?


No research on
woman


… but brain scans are a relatively new research technique


each new study adds to our body
of knowledge



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ANALYSIS

Nature

Are


London taxi drivers born with unusual brains?


Nurture

Do


London taxi drivers develop unusual brains?
(see Maguire et al 2000, in Banyard p158)


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CAN YOU EVALUATE THIS STUDY?

in terms of…


experimental validity (control of variables)

ecological validity (realistic task)

external validity (generalisation)

ethical validity

reliability (replication, objectivity)

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REVIEW

Where was/were the


experimental design


IV


DV


Factors of interest


Method/procedure


Main results/findings


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