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Navigation-related structural change in the hippocampi of taxi drivers 3FA3- Module 4 Group A5 Swiya Nath Preeyam Randeria Catherine Leslie Tapiwa Musewe.

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Presentation on theme: "Navigation-related structural change in the hippocampi of taxi drivers 3FA3- Module 4 Group A5 Swiya Nath Preeyam Randeria Catherine Leslie Tapiwa Musewe."— Presentation transcript:

1 Navigation-related structural change in the hippocampi of taxi drivers 3FA3- Module 4 Group A5 Swiya Nath Preeyam Randeria Catherine Leslie Tapiwa Musewe Nicholas Hawkes

2 Table of Contents Target Article Background Information Critique Subject Selection ▫Sex Bias Critique Methods Alternative Results Conclusion

3 Target Article Aim : Test adult plasticity Method: Compare taxi driver’s brains to control subjects’ Conclusion: Adult hippocampus is plastic Swiya Nath

4 Table of Contents Target Article Background Information Critique Subject Selection ▫Sex Bias Critique Methods Alternative Results Conclusion

5 Hippocampal size related to foraging behavior Food storing species Bird species that store food have higher relative hippocampus size Swiya Nath

6 Hippocampal plasticity related to season of foraging Storing Retrieval Number of large cells in anterior hippocampus increase during August Number of large cells in hippocampus increase during October Swiya Nath

7 Table of Contents Target Article Background Information Critique Subject Selection ▫Sex Bias Critique Methods Alternative Results Conclusion

8 Age Variance Average age = 44 years Range = years Not an accurate representation of the wide age group Preeyam Randeria

9 Training Variance Licensing training lasted = 10 months to 3.5 years Average time spent before passing the licensing test = 2 years Amount of time spent on training can affect spatial development Preeyam Randeria

10 Experience Variance Years of experience ranged = 1.5 years to 42 years Average years of experience = 14.3 years Too large a range, leads to inconsistency Divide the years of experience into two ranges Preeyam Randeria

11 Control Group’s Experience Driving experience of the control group was not calculated More driving experience would result in a larger spatial capacity Preeyam Randeria

12 Selection Bias MRI scans from control group was used to compare hippocampus sizes Record scans were used thus MRI scans were conducted for some deficit or problem Not representing the general population Preeyam Randeria

13 Socio-Economic Status (SES) SES was not identified for drivers or the control group Control Group: lower SES might take public transportation more often and do not drive Drivers: different SES might depend on the type of area one works in Preeyam Randeria

14 Cause and Effect Did not measure or have records of the hippocampus size before the licensing training These individuals became taxi drivers because they were naturally better at spatial memory or vice versa? There is evidence for a correlation but not for a causal relationship Preeyam Randeria

15 Uncontrolled Variables Education Level ▫Based on education pursued, the taxi driver might already be used to memorizing Similar limitation with control group and between the control group and taxi drivers Preeyam Randeria

16 Control Subjects 16 control subjects taken from a group of 50 Group of 50 came from MRI scan Database Not a random group of people Catherine Leslie

17 Table of Contents Target Article Background Information Critique Subject Selection ▫Sex Bias Critique Methods Alternative Results Conclusion

18 Sex Differences Study cannot be generalized. It has been proven that men and women are different in terms of spatial ability Differences in spatial functioning Differences in brain anatomy Catherine Leslie

19 Spatial Functioning Components of Spatial Function Spatial Visualization –Mental rotation Spatial Perception – Water level task Spatial Memory – Visual features vs. location Spatial Orientation – Difference in used cues Catherine Leslie

20 Brain Anatomy MenWomen Higher % of Working memory and cerebral spinal fluid Higher Amount of grey matter in left hemisphere Asymmetries Higher % of grey matter No asymmetries Sex differences in brain anatomy may be able to explain differences in behaviour. Catherine Leslie

21 Table of Contents Target Article Background Information Critique Subject Selection ▫Sex Bias Critique Methods Alternative Results Conclusion

22 Inter-rater Reliability Would strengthen results if corresponding measurements were found by multiple experts. ProsCons Eliminates rater - rater ambiguity Only measured by one expert Human errors Precision 24 X 32 Measurements Tapiwa Musewe

23 Restrictive Selection All participants were right-handed Prevented age-scale cluster Eliminated individual anatomical differences by creating one template Participants were all male Tapiwa Musewe

24 Test – Retest Reliability Used three different approaches to analyse volumetric changes in grey matter Magnetic Resonance Imaging (MRI) ▫Provides detailed images of soft tissues in the brain Voxel-Based Morphology (VBM) ▫Useful for determining neuroanatomical differences between individuals ▫Allows anatomical differences of focal regions of the brain to be analysed rather than volumes of the whole brain Pixel counting ▫Volume of hippocampus calculated by logical calculations Tapiwa Musewe

25 Table of Contents Target Article Background Information Critique Subject Selection ▫Sex Bias Critique Methods Alternative Results Conclusion

26 Results Swiya Nath Posterior hippocampus larger for taxi drivers than control subjects Anterior hippocampus larger for control subjects than taxi drivers Results more drastic in left hemisphere Adults show plasticity

27 HIPER Model Anterior HippocampusPosterior Hippocampus Smaller for taxi drivers than control subjects Larger for taxi drivers than control subjects EncodingRetrieval Do taxi drivers have more experience with spatial memory, or simply retrieval as the HIPER model suggests ? Swiya Nath

28 Taxi Driver with Bilateral Hippocampal Damage BUT lesion not isolated to posterior hippocampus RetrievalEncoding Well on spatial information (landmarks) Poor in actively navigating novel neighbourhoods Well on main roadsPoor on detours Swiya Nath

29 Conclusion Selection bias = Randomized selection Sex bias = Lacks generalizability Test retest reliability HIPER model = Other memory test


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