Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MBE > Brain evolution and PFC fractionation > Flashcards

Brain evolution and PFC fractionation Flashcards

You may prefer our related Brainscape-certified flashcards:
MBE flashcards
1
Q

Brain volume

A

Steadily increased relative to body weight in homo-lineage by a factor of approx. 2 from 2 million years ago.
(Lewin & Foley, 2004).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Human brain no bigger than it should be

A

Reached current size approx. 100,000 years ago.

Symbolic developments occurred 50k to 40k years ago.

Brain size is not everything.
- among humans, only small proportion of intelligence differences attributed to size. (Rushton & Ankey, 2009).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Paleoneuroanatomical evidence

A

Hominin cranial fossils preserve evidence of:

  • overall brain size.
  • cerebral asymmetry.
  • cortical sulcul patterns - leaves impressions on the endocra surface.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Fossils suggest 3 major stages of hominin brain evolution

A

Stage 1 (3.5-2mya):

  • brain reorganisation without substantial expansion - includes relative expansion of posterior parietal association cortex at the expense of the occipital cortex.
  • may have been important for emergence of stone tool making by 2.6mya (Semaw et al, 2003).
  • some suggest stage 1 involved in prefrontal lobe shape (Falk et al 2000).

Stage 2 (2-0.5mya):

  • sudden increase in brain size associated with appearance of homohabilis.
  • followed by gradual expansion related to body size increases in homo-erectus.
  • first appearance of modern human like cerebral asymmetries in hobo habilis including enlargement of the Broca’s cap region in left LPFC (BA44).
Stage 3 (0.5-0.02mya):
- past 15k years decreasing body size brought human mean brain size down a bit.

Overall (excluding Broca’s area cap enlarging) evidence of frontal lobe size and reorganisation is limited.
- fractionated function.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Evidence from comparative neuroanatomy: relative size of the frontal cortex?

A

Differences are large in size of FC between humans and primates.

  • but FC in humans and great apes occupies a similar proportion of the cortex of the cerebral hemispheres (Semendeferi, Schenker & Damasio, 2002).
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Evidence from comparative neuroanatomy: frontal vs. prefrontal

A

Not relative size of the frontal cortex but of the PFC - evidence of PFC reorganisation.

Prefrontal area argued to be fractionated (a substance is divided during phase transition into smaller quantities). in 1 of 3 ways:

  1. presence of granular layer 4 (Stellate and other smaller cells).
  2. projection area of the mediodorsal nucleus of the thalamus.
  3. motorically “silent” area when stimulated.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Evidence from comparative neuroanatomy: larger in humans

A

Human PFC especially enlarged compared to great apes - Passingham & Smaers (2014).

BA10 (Polar PFC) is larger in humans relative to the rest of the brain than in apes - Semendeferi et al (2001).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Cytoarchitectonics & granular cells of the PFC: granule cells

A

= interneuron.
- defined by its smallness.

Benefits of size:
- density and number of connections.

In the PFC: only primates have granular layer 4 in PFC.

  • thickness of layer 4 increases as one foes from caudal to rostral along the medial and orbital surfaces of the frontal lobe.
  • area can be agranular enough to warrant exclusion from special status even if some granule cells present.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Cytoarchitectonics & granular cells of the PFC: cerebral cortex layers

A

Cerebral cortex = outer layer of cerebrum/cortex.

  • largest and most prominent part of the brain.
  • cerebral cortex has 4 lobes.

Layers:

  1. molecular layer.
  2. external granular layer.
  3. external pyramidal layer.
  4. internal granular layer.
  5. internal pyramidal layer.
  6. multiform layer.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Cytoarchitectonics & granular cells of the PFC: phases of evolution of the PFC

A

Early mammals develop agranular areas of PFC: medial and orbital PFC/insular cortex.

  • primates alone have granular cortex.
  • rats only have agranular PFC.

Lateral and polar granular PFC last to appear during anthropoid evolution.

Granular PFC appeared in early primates as they adapted to life confined by trees - caudal PFC and areas of OPFC:
- function in the assessment of value or primary reward (e.g. food - Passingham & Wise, 2012).

Several new granular PFC areas appeared during anthropoid evolution - grew larger, foraged more (by reducing choices that increased risk of predation or wasted effort), became dependent on food and vulnerable to falls:

  • dorsal PFC (BA9/46).
  • ventral PFC (BA45/47).
  • polar PFC (BA10).

Lateral and polar granular PFC - last to appear during anthropoid evolution.

Brain became wider and more rounded at the front during homonoid evolution.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Cytoarchitectonics & granular cells of the PFC: what did granular PFC add?

A

Evolved to implement new, faster, general-purpose mechanism - in response to adaptive pressures.
- supports older, reinforcement-learning mechanism.

Granular PFC generates goals appropriate to goals and needs.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Cytoarchitectonics & granular cells of the PFC: dorsal paracingulate cortex connects to dorsal PFC

A

Modern humans probably evolved after Broca’s expansion seen in homo habilis.
- when frontal lobe PFC reached modern state - before advanced tool use, abstract thought, language etc (approx. 70-40kya).

Elston et al (2006): granular cortex is 80% in humans and 55% in chimps.

Elston et al (2001): pyramidal cells in layer 3 = 70% more spinous in humans then monkeys.

Schenker et al (2005): human PFC has larger volume of short nerve fibre connections connecting parts of PFC.

Areas of human specialisation (at cell level of PFC):
- broca’s area (BA 44/45).
- lateral part of the polar PFC (BA 10).
- dorsal anterior cingulate/medial PFC (BA 32).
> BA 10 and BA 32 lack homologues in monkeys.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Cytoarchitectonics & granular cells of the PFC: connections

A

PFC = brains controller.
- has connections.

Synaptogenesis last longer in PFC =than other regions (Bianchi et al, 2013; Levitt, 2003).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Cytoarchitectonics & granular cells of the PFC: brain development, mirrors brain evolution

A

Cortical expansion during evolution matches expansion during development (Hill et al, 2010).

Ultimately, newer PFC regions (lateral and polar) are better learning devices (Passingham & Wise, 2012).

Leaves us more open to cultural influences than other species whose brain stops developing earlier and are more influenced by genes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Cytoarchitectonics & granular cells of the PFC: abstraction increases with granularity

A

Processing hierarchy in brain (Badre, 2008):
- posterior
> anterior
> caudal
> rostral.
- processing moves from concrete to abstract.

Granular PFC at the apex of processing hierarchy (Passingham & Wise):
- allowing integration of all info necessary to generate goals from current context and events based on knowledge of current value.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Cytoarchitectonics & granular cells of the PFC: PFC summary

A

Brain got wider and more round at front.
- lateral and polar regions (populated by granular cells) - during hominoid evolution.

Regions of PFC enlarged compared to other apes:
- particularly BA10.

Evidence of frontal lobe changes during hominin evolution:
- particularly in Broca’s cap in lateral PFC which would have widened brain further.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Orbitiomedial regions of the PFC

A

Independent variation in size of FC areas across hominoids (Bonobos, chimps, orangutans and humans):

  • dorsal (Schenker, Sedgouttes & Semendeferi, 2005).
  • polar (Semendeferi, Armstrong, Schlicher, Siller & Van Hoesen, 2001).
  • orbital (Semendeferi, Armstrong, Schlicher, Siller & Van Hoesen, 1998).

Variation correlates with behavioural differences between species:
- suggests degree of evolutionary independence between LPFC and VMPFC (Stout, 2010).

18
Q

Orbitiomedial regions of the PFC: orang-utans

A

Unusually small orbital frontal cortex.

Solitary and simple organisation (Schenker et al, 2005; Semendeferi et al, 1998).

19
Q

Orbitiomedial regions of the PFC: Phineas Gage

A

Impaled through frontal lobe.
- hardworking, energetic, clear thinking -> impatient, rude, angry etc.

Lateral PFC untouched.
Medial PFC wall destroyed and some of BA10 - suggests involvement in controlling anger and organisation.

20
Q

Orbitiomedial regions of the PFC: orbital and VMPFC - reward

A

Shown human orbital PFC conveys info about expected rewards (London et al, 2000; Rolls et al, 2008).

Damage to orbital PFC - disturbance in learning and decision making tasks involving reward evaluation (Rolls, 2000; Bechara et al, 1994).

IOWA/Bechara gambling tasks:

  • select from difference decks to receive rewards or penalties.
  • some decks give good rewards but heavy penalties vs. moderate rewards for small penalties.
  • orbitofrontal patients don’t avoid selecting heavy penalty piles.
21
Q

Orbitiomedial regions of the PFC: early damage to prefrontal cortex

A

Impairment of social and moral behaviour related: Anderson et al (1999):

  • normal upbringing, no family history of psychiatric disease, socially well adapted siblings.
  • normal neurological profiles in both patients except for behavioural defects.
22
Q

Orbitiomedial regions of the PFC: reward and OFC

A

VMPFC seems important in reward/punishment processing.

Warm, pleasant feelings associated with activity in brain - Rolls, Grabenhorst & Parris (2008).

23
Q

Orbitiomedial regions of the PFC: financial rewards/losses

A

More lip up representations when receiving rewards but still some activity for punishment in human OFC. (O’Doherty, Kringelbach, Rolls, Hornak & Andrews, 2001).

24
Q

Orbitiomedial regions of the PFC: OM regions summary

A

Involved in socialising, control of emotions, reward processing:

  • eg. warm pleasant feelings.
  • Phineas Gage.

Involved in simple decision making prevents risky and silly behaviour:
- eg. gambling tasks.

Little evidence for relative expansion at any stage during hominin evolution.

25
Q

Lateral PFC

A

Large in orangutans and chimps, small in bonobos - use tools; bonobos do not (Van Schaik, deanem & Merrill, 1999).

LPFC supports instrumental action (Stout, 2010).

26
Q

Lateral PFC: also involve in action regulation

A

Wisconsin card sorting test (Grant & Berg, 1983; Brenda & Miller, 1963): patients sort by experimenter’s rule.

  • rule determined by first card placement.
  • experimenter says yes or no.
  • after acquiring rule, it is changed.

Lateral FC activated by switch dimension (Konishi et al, 1998).

27
Q

Lateral PFC: maintaining task relevant info in working memory

A

If PFC represents rules, it must be able to sustain them in the face of interference.

Studies shown neurons within LPFC remain active during delay between a cue and later execution of a response (i.e. working memory). - Fuster, 1971; Kubota and Niki, 1971.

LPFC evolved as an anterior extension of motor cortex and plays a role in action regulation (Fuster, 97).

28
Q

Lateral PFC: action regulation and maintaining rules in working memory

A

MacDonald et al (2000) - dissociating the role of the DLPFc and anterior cingulate cortex in cognitive control.

Stroop task - subjects alternated between naming ink colour and word colour.
- DLPFC maintains task instructions in working memory.

29
Q

Lateral PFC: rule based action control

A

Damage to VL areas impairs the ability to learn or switch between action rules.

  • in monkeys (Alsband & Passingham, 1985).
  • and humans (Hodgson et al, 2007) - inability to bias correctly.

Patients with LPFC damage make errors when applying action rules during the Wisconsin card sorting task.

30
Q

Lateral PFC: Broca’s aphasia

A

Loss of ability to produce spoken language.

  • non-fluent aphasia.
  • speaking requires control (articulation).
31
Q

Lateral PFC: lateral PFC summary

A

Action regulation: extension of motor area (Bonobos don’t use tools).

Maintaining active rules: working memory.

Speech production: action control.

Mental flexibility: rule switching (lesions cause inability).

Expansion during evolution: good evidence.

32
Q

Polar PFC (BA10)

A

The more anterior lateral regions are expanded and reorganised in humans - Rilling, 2006.

BA10 = most anterior portion of PFC - enlarged in humans and contains less densely packed cells that leave more room for connections (Semendeferi et al, 2001).

33
Q

Polar PFC (BA10): BA10 - Brodmann area 10

A

Anterior most portion.
Cannot identify boundaries.
Does not include all parts of the PFC.

In humans, larger in relation to the rest of the brain than in apes.

Granular layers: more space available for connections with other higher order association areas.

34
Q

Polar PFC (BA10): Burgess, Scott, & Frith (2003)

A

Ppts carry out action after delay.

  • lateral regions: showed increased activity during delay (working memory).
  • medial regions: showed decreased activity.

Lateral BA10 = maintains intention - internally-generated thought.
Medial BA10 = suppresses it.

35
Q

Polar PFC (BA10): prospective memory

A

Lesions in area 10 associated with planning of future actions, undertaking initiative and multitasking (Okuda et al, 1998).

Patient AP (Shallice & Burgess, 1991) - complete removal of rostral PFC:

  • IQ, memory and attention = normal.
  • tardiness and disorganised.
36
Q

Polar PFC (BA10): gateway hypothesis of BA10

A

Prospective memory: (intention to act) = internally generated thought.

Burgess et al (2005) : BA10 responsible for switching between stimulus-driven and internally-driven thought.

Lateral BA10: maintains intention during delay (working memory) and lateral for action control.

Medial BA10: suppresses internally generated though to permit focusing on external environment.

37
Q

Polar PFC (BA10): BA10

A

Organisation of behaviour: eg. Phineas Gage, AP etc.

Working memory: along with lateral PFC.

Lateral regions: acts as working memory for intention.

Medial suppresses lateral: to permit externally driven thought.

Good evidence for expansion during evolution.

38
Q

Rostro-caudal (Abstract-concrete) distinction in PFC

A

Neuroscientists have often fractionated lateral PFC into levels in an action control hierarchy (Badre, 2008).
- with more rostral regions supporting more abstract action rules (Badre & D’Esposito, 2009).

Consistent with evidence of rostro-caudal architectonic connectional and developmental gradients in PFC (Badre & D’Esposito, 2009).

But exact functional nature remains controversial about:

  • domain specificity (Petrides, 2005).
  • relational complexity (Christoff & Gabrieli, 2000).
  • temporal context (Koechlin & Summerfield, 2007).
  • representational hierarchy (Badre & D’Esposito, 2007).
39
Q

Summary

A

Orbito and medial regions of PFC - involved in reward for processing, control of emotions and social skills.

Lateral regions - involved in action control including articulatory movements (Broca’s cap in BA44), rule representation and application.
- also involved in working memory.

Polar PFC regions - expanded and reorganised in humans, confers greater capacity for abstract thought, WM etc.

40
Q

Summary: wider and rounder at the front

A

Lateral and polar granular regions most recent region in primate evolution.

Evidence for expansion for Broca’s area during hominin evolution.

Expansion of PFC areas across evolution conferred upon us:

  • greater action control (manual and vocal).
  • working memory capacity (LPFC & BA10).
  • greater capacity for abstract thought (BA10; Polar PFC).
41
Q

Polar PFC (BA10): lateralisation in hominins

A

Some lateralisation in monkey and apes but not major (Poremba et al, 2004).

Lateralisation = idea that each hemisphere has functional specialisations.

In humans it is an organisational principle:

  • language functions (Corballis, 2005).
  • high level organisation of action production (De Renzi & Luckelli, 1998)
  • certain prefrontal functions (Shallice, 2004).
  • some perceptual functions (Warrington & Taylor, 1978).

MBE (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions