Lecture 8 - sex/gender differences: brain function Flashcards
1
Q
sex/gender differences in brain function
A
- fucntional cerebral asymmetries
- task related brain activity
- functional connectivity
- task related connectivity
- resting state connectivity
2
Q
functional cerebral asymmetries
A
- FCAs investigated in several ways: clinical studies of patients with unilateral lesions, behavioural studies of healthy pp’s, neuroimaging during lateralised tasks
- FCAs show the asymmetrical rep of a specific cog process to one hemisphere. looks at difs in the amount of brain activity
> L hem = sensory stimulus from r body, motor control of r, speech langauge & comp, analysis & calc, timing & sequences, recognition of words
> r hem = sensory stimulus from l side of body, motor control of l, creativity, spatial ability, context/perception, recognition of faces places & objects
3
Q
sex/gender differences in FCAs clinical evidence
A
- early studies show evidence for l and right lateralised task
> Mcglone et al. verbal IQ lower in Lh lesions in male pp’s but injury to rh did not impair langauge ability. in f, doesnt matter where lesion is they perform worse than controls in verbal IQ = m brain more lateralised to the left
> Mcglone & Kertesz: examined spatial impairments follow unilateral brain injury. men with rh lesions poorer performance than men with lh lesions and women with rh lesions. object & spatial recognition thought to be in rh. female intact performance regardless of damage to hems. in women the non-lesioned hem can support the specific cog task. so women are mor bilateral and men more lateralised. men rh more to do with spatial processing & lh for language.
4
Q
sex/gender differences in FCAs: behavioural evidence
A
- e.g. dichotic listening tasks & right ear adv.
> weekes et al. (1995) - women smaller rea than men due to smaller right ear scores. high masc men had low LE and higher RE scores than low masc men. degree of lateralisation cor with sex role identification & males reported more from right eat than le. - meta analysis shows males more lateralised than females
- hodgetts & hausmann (2022) several studies also show no gender/sex difs for language related FCAs. but effect sizes typically small and need meta analyses.
- tasks can also measure FCAs in emotion recognition & visuospatial processing
> emotional primary face task 0 ask pp which of two faces has more stronger facial expression. typically L stimuli has more adv as processed by r (emotion areas)
> poverbio et al (2010) used EEG for FCAs in face processing. results showed larger rh responses to faces in men. faces espec emotional are more lateralised to r but females similar activity between hemispheres - FCAs not fixed and can change in short intervals
5
Q
sex hormones across menstrual cycle
A
- during menstruation both sex hormones are lowest. after oestrogen levels inc and peak at day 14 while progesterone stays flat.
- during luteal progesterone inc while oestrogen dec
6
Q
sex hormones and FCAs
A
- Hodgetts et al (2015) - FCAs in women differ depending on their current hormone levels. high levels of oestradiol reduce language lateralisation (less asymmetry) = whether or not you find an FCA may depend on cycle phase.
7
Q
task related brain activity
A
- men typically better at mental rotation
- women typically better at verbal fluency
8
Q
sex/gender and task-related brain activity: mental rotation
A
- Jordan et al (2002) - women showed significant bilateral activity in intraparietal sulcus, superior and inferior parietal lobe, inferior parietal sulcus and premotor areas
- men exhibited activation in r parietal-occipital sulcus, left infraparietal sulcus and left superior parietal lobule. BUT no performance difs between men and women. = use different strategies to complete the task.
- pathways for solving mental rotation tasks: 1. primary visual area 2. extrastriate cortex 3. inferior temporal or occipital regions 4. parietal regions 5. premotor cortex
- men showed signif stronger parietal activation while women greater right frontal activation
9
Q
sex/gender and task-related brain activity: cognitive control
A
- Koch et al (2007) m and f completed n back task in either neg emotion condition or neutral condition. neg emotion induction = impaired wm in both m and f.
> m: wm under neg emotion associated with prefrontal and parietal areas
> f: under negative emotion induction showed inc activity in amygdala & ofc
= sex/gender difs in interaction of cog and emotional processes
10
Q
functional connectivity
A
- ## defined as the statistical association or dependency among two or more anatomically distinct time series
11
Q
sex/gender and functional connectivity: mental rotation
A
- Butler et al. (2006) - f greater activity in dorsalmedial pfc (more top down effortful processing) m greater activity in basal ganglia, precuneus and sensory cortices (bottom up automatic processing)
- ## accurate mental rotation was associated with deactivation of parieto-insular vestibular cortex in men
12
Q
sex/gender and functional connectivity: emotion & cognition
A
- Butler et al (2007) - f showed suppression of activity in vantral ACC (responsivle for emotion reg and coord stress) & inverse cor of ventral & dorsal anterior cingulate cortex = sex/gender difs in task related functional connectivity reflect difs in strategies to complete task
> suppression of ventral anterior cingulate reflects greater cog effort consistent with top down approach
13
Q
resting-state functional connectivity
A
- investigated difs in functional connectivity in absence of a specific cog task
- Biswal et al (1995) - low freq oscillations of fmri bold signal reflect spontaneous neural activity.
> can see functional connective networks that exist when brain is resting - become more active in tasks - DMS important here - it becomes less active when engaging in a cog task
14
Q
sex/gender and functional connectivity: resting state networks
A
- sex/gender difs in default mode network: comprised of dorsal & ventral medial pfc, posterior cingulate cortex, precunus and lateral parietal
- thought to underpin spontaneous cognition but also integrates processing across multiple networks.
- activity in dmn typically dec during specific cog processing
15
Q
sex/gender and functional connectivity: default mode network
A
- several studies suggest stronger functional connectivity in the DMN of women compared to men
- but other studies reported no sex/gender differences
- possible reasons for inconsistencies: analysis method, overlap in sex/gender difs
16
Q
resting state connectivity and the human brain mosaic
A
- Weis et al (2020) - used machine learning to assess how accurately an AI algorithm can classify brains as m or f
> whole brain classification accuracy 75-65% but pronounced difs in prediction accuracies of specific brain regions indicating spatially specific effects - suggests the functional connectivity of specific regions in brain that is most different between m and f
> no region 100% supporting that brain is not sexually dimorphic & supports mosaic - functional activity can vary across menstrual cycle
17
Q
sex hormones and resting state connectivity
A
- some studies showed sex/gender difs in rsfMRI but consistency is low. homone fluctuations?
> women show higher functional connectivity in two resting state networks espec frontal. but no effect of cycle phase - dif results found by weis et al (2019)
> for dmn functional connectivity was stable in men but fluctuated in women
> inc connectivity in left pfc during menstrual phase vs other cuc;es
> for auditory network sex/gender dif was found (higher connectivity in m)
18
Q
what causes sex/gender differences in the brain
A
> genetics
organising / activating effects of hormones
socially derived gender roles
gendered dev trajectories
- but inc no. studies support idea that sex/gender difs in brain are a product of several interactive factors including bio and socio-cultural environmental influences.
