Lecture 12/13: Comparative Neuroscience approach Flashcards
What is the field of Comparative neuroscience doing? What is the comparative approach to Human Cognition and Brain?
* To figure out why our minds and brains are the way they
are (raison d'être), by comparing them with other species.
* Determine homologies (i.e.what is common)
* Determine differences (i.e. what makes us unique)
* Not only looking at brain structure. Interested in understanding how certain functions (i.e. speech) emerge through primate evolution.
What is one of the main cognitive processes that we have that distinguishes us from animals?
Language
What is the goal of comparitive neuroscience?
Perform anatomical studies of brains across different primate species in order to unnderstand what is so specal about the human brain.
Our brain has a lot of similarities with which family of species
Ape family: bonobos, chimps, orangutans
Why does the primate evolution not proceed like this: monkey → ape → human
We cannot say that the evolution goes like monkey evolves into ape into human.
The clearest reason for this is that we all exist together at the sime time in this world. We have each a final way to adapt to the environment of this world.
What is the true picture of evolution?
The primate phylogeny
* We share a common ancestor apes and monkeys 63 million years ago.
* We branched off from the chimps
* Primal evolution is not linear
Evolution of speech control in the human cortex
- The brain regions that are involved in spech in the human brain exist in the macaque → common speech/ vocal frontal areas in the human and macaque brain.
- The regions that we think are critical for speech, actually exist in mammals that do not speak. → So we want to know what these regions are doing in non human primate brain.
There are two main evolutionary theories for why we speak and monkeys do not, name and explain the first hypothesis.
- Peripheral hypothesis: They cannot speak because their vocalization apparatus (their vocal tract) does not allow them to produce the same set of sounds that we need in our speech. Most of this evidence comes from Liberman: he concluded that based on the vocal space, in the macaque vocal tract, they are not able to produce the range od sounds needed for speech.
Fitch experiment in 2016
Fitch redid the experiment that Lieberman did. He collected X-ray pictures of the macaque and he did a more high tech modernization of the vocal range. He found that the range of the macaque vocal track was actually a lot bigger than what Lieberman had shown.
Based on this study, he showed that the vocal track of the macaque monkey is actually capable of producing the range of vowels needed for human speech.
This experiment destroyed the whole theory that the monkeys are limited by the vocal track differences.
There are two main evolutionary theories for why we speak and monkeys do not, name and explain the second hypothesis.
- Neural Hypothesis: The neural systems that are involved in controlling this vocalization (vocal apparatus) is different. It evolved in humans to enable speech.
“The lower animals differ from man solely in his almost infinitely larger power of associating together the most diversified sounds and ideas; and this obviously depends on the high development of his mental powers.”
The neural systems involved in cognitive vocal control evolved in humans to support the emregence of speech.
Speech areas in the human (Penfield)
These are the areas that were identified from Wilder Penfields experiements (awake brain stiumulation).
- The ventrolateral frontal cortex and the medial frontal cortex are both important for vocalization.
- To identify the areas invovled in higher order control of speech: areas that caused speech interference and arest (ventrolateral frontal cortex, Brocas area, dorsal medial path, wernickes areas).
Name and explain the role of the speech areas in the human frontal cortex
Area 44 (pars opercularis)
* Broca’s area (posterior part)
* Critical (?) for speech and language –> further research shows that it might not be as important as we think.
Mid-Cingulate Cortex
* Increased activity during voluntary speech production (e.g. Paus et al, 1993).
* Stimulations evoke urge to vocalise, and sometimes
emotional vocalisations.
Supplementary and pre-supplementary motor areas
* Stimulations evoke vocalisations. (Penfield and Roberts, 1959)
Dorsomedial frontal network
* Verbal fluency impacted only when lesions involved both MCC + preSMA/SMA regions.
* Petrides and Chapados studied many patients with frontal lesions. They studied what are the typical patterns of lesions that will lead to problems of verbal fluency (ability to produce speech fluently). They found that only when patients have lesions covering both the MCC and pre-SMA/SMA it will lead to problems with verbal fluency. This set of regions function as a network in the control of speech.
Do nonhuman primates have voluntary vocal control?
Recent evidence that suggest that non-human primates have voluntary vocal control:
1. Context-dependent calling: when they are producing their calls, they are producing certain calls under certain situations and other calls in other situations.
- low quality food = cou
- better food quality = harmonic arch
- Diferent calls for different predators (land base vs sky base)
They only make these sounds if there are other monkeys around here. This tells us that they have somee sort of direct control over their vocalization.
- Voluntary vocal control (german researcher - Stefan Hague)
- Managed to train 2 monkeys to actually switch between different call based on arbitrairy queues. Will express different calls when they see a white square vs red vs blue.
- they can only use very limited innatte calls that are already part of their natural repertoire. - “Novel” vocalizations
- the monkey is reacting based on the feedback (the vocal vocalizations from a human), so they can interpret what we are saying. They can produce a smile and rasperries (a sound) both of these involving high level control of their mouth. Rasperries = a sound only found in captive chimpazees so use it to get people to feed them.
- In apes, we see the ability to produce a new combinattion of oral facial and vocal vocalizations and use them to achieve certain goals.
apes = tails
monkeys = no tail
What might be its common/basic role across humans and nonhuman primates? How has is changed?
The set of brain regions critical for human speech production exists also in the macaque, and are involved in
cognitive vocal control.
What is the hypothesis for the common role of area 44 across humans and monkeys?
Area 44: Conditional selection between vocal and orofacial motor actions.
This hypothesis comes from anatomical work that in thee lateral frontal cortex (Petrides and Amiex).
Dorsal posterior lateral frontal cortex (pLFC): Selection of hand actions via conditional rules
Rostro-caudal organization in the pLFC: Conditional selection area is rostral to the respective motor-effector
area
Lesion in green area = monkeys are no longer able to produce a task called conditional hand moto-selection test: produce one hand action when they see one queue and produce another hand action when they see another queue. Conditional selection = performance of hand action A and B based on some visual queue.
They showed the same thing in humans using fMRI experiments. The same area started to light up.
Conclusion: In both humans and monkeys this area is involved in the selection between hand actions and is situated directly anteriror to the primary motor representation of the hand. More studies showed that in both when subjects had to decide between different circuits (to the left or right) based on visual cues, this area is activated (conditional saccadic area) and is located directly rostral to the frontal eye fields (brain region involved in producing circuits).
Area 44 – conditional visuomotor selection of vocal and orofacial actions –> involved in selection between the vocal and orafacial actions.
What is the hypothesis of the common role of the mid-cingulate cortex across humans and monkeys?
Mid-Cingulate Cortex: Monitoring behavioral feedback for adaptations (adpating ones behaviour).
Experiment: Problem solving task
Put the monkey in front of a screen and he is shown four dots. He has to find which dot will give him a reward. Put electrode on MCC –> record neuron activity.
Increased MCC activity following:
1) Incorrect feedback (informs him to change his response)
2) First correct feedback (informs him to keep chosing this one)
But NOT for subsequent correct feedback (after he gets the first correct feedback) …
Conclusion: The MCC is something in your brain telling you of the need to adapt your subsequent behaviors.
Same task in humans = same thing.
What are the experimental conditions of the the learning task to study different possible conditions.
Constructed 4 different versions of the task. The structure is the same –> they have to learn conditional associations but now we want them to produce different types of actions: speech, verbal, manual, orofacial. Test when different responsed are involved to see differential activations in different areas.
The reason for the two feedback types is to see if the MCC dissociates between speech and nopn speech (vocal feedback).
Results: Post-learning phase, response selection between different responses.
Manual: activation in dorsal premotor cortex, none in area 44
Vocal/verbal: Activation in area 44, none in dorsal premotor cortex
Orofacial: activation in area 44 and dorsal premotor cortex. We actually see dorsal premotor activation which is asociated with hand –> maybe it is an intermediate between hand and vocal production.
Area 44: Conditional selection of vocal and verbal actions
Dorsal premotor area: Conditional selection of hand actions
Both: Conditional selection of orofacial (mouth) actions (?)
Sulcal-based localization of response selection peaks in individual subjects
We wanted to know whether we can predict based on individual or sulcal patterns where these locations are. Tedious work where you label all the activations in individual subebjects.
Result: When subjects are selecting between different hand movements, you will see activation in the green region (sprs-d)
When they are selecting betweeen different oralfacial, vocal or verbal actions, you will see activations in the blue region.
We can study the pattern of cortical folding, we can actually start making predictions of where certain functional areas are.
Summarize the orofacial-vocal control network that has evolved across primates to enable human speech
black area (area 4): increased activation when subjects are deciding between manual and orofacial responses.
Red area (44): activated when subjects are doing conditional selections between mouth, orofacial and verbal actions.
Blue area (MCC): when subjects are paying attention to vocal feedback, there is activation in the MCC for learning associatiations.
PreSMA: something unique that appears when we have to deal with verbal speech related feedback.
Area 45: when subjects were learning verbal associations, there is an activation in are 45.
Area 45 and Pre SMA could be potential specialization for human speech
Common space 1 - cytoarchitecture
- The neocortex can be divided into 6 cortical layers.
- Brain areas can be distinguished based on the organization and appearance of the cell layers.
- Brodmann identified his map on different patterns of layering.
- Homologous brain areas can be defined across specied based on cytoarchitecture. Example: Primary area 4 is defined by giant pyramidal cells (Betz cells) in layer V. The criteria for defining area 4 in any species is that is has large cells in layer V of the cortex.
Conclusion: Defining homologous areas in the human
and monkey frontal cortex using common cytoarchitectonic criteria. (Petrides and Pandya, 1994; 1999)
Provides a common ground for bridging human-macaque investigations of frontal lobe anatomy and function.
Connectivity: the connectivity blueprint approach
The Connectivity Blueprint Approach
1. A common set of white matter tracts that can be extracted across primate species using diffusion-based MRI.
2. For each region in an individual brain, we can then compute its pattern of connectivity with the same set of white matter tracts – i.e. its unique connectivity fingerprint.
3. We can then compare brains across species based on their connectivity fingerprints defined by the common tracts.
Common space 3 - Cortical folding
- Cortical folding across primate species is not random, and follows a topographical organization! There is a relationship between the primate brain and the locaion of the main functional areas in the brain.
- Common folds exist across species, and can serve as landmarks for anatomical and functional areas.
- These common folds could then serve as landmarks for interspecies cortical comparisons.
