PSY352H5 Lecture Notes - Lecture 4: Complex Differential Form, Acetylcholine, Esterase
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Lecture 4
Proximate questions: How things work in the brain?
Stimulus ->
perception -> processing -> motor command
• behavioural response
• there is stimulus outside in nature and based on the processing, the brain comes up with a
response and comes up with connections
• based on these changes in connections it leads to a behavioral response
• some behavioural responses are very complicated so we don’t fully understand
everything yet
• but even the most complex behaviours can be explained by neurobiological outputs in the
brain
• genes do influence a lot of behavior
• there is some findings that genes provide predispositions to certain types of behavior but
they are not the sole cause of behavior
• between the nucleotide sequence and behavior there are so many different steps which
suggest that there is no direct link between genes and behavior
o which is why when we say that there is a gene for aggression it over simplifies the
interaction between genes and behavior
• the reason why genes are so important because they encode certain types of information
• the nucleotide sequence of a gene determines the amino acid sequence of proteins
• but depending on how you read the change, you can transcribe different mRNA and
proteins from it
• the nucleotide sequence tells you what proteins you can make
• the amino acid sequence will tell you what the protein will look like
o the positive and negative ions will make the amino acid wind up into a specific 3d
shape
• the 3d structure of the protein will affect the function of the protein
o eg. A binding protein or maybe it will have a different function
• when the proteins interact with each other it can make biochemical pathways very
complicated
• it can effect
o how the embryo is formed
o how to develop neuronal circuitry and anatomy
o it all influences each other which in turn affects behavior
• shows a protein and different pockets
• it can bind to different types of proteins
Biochemical pathways
• shows how complex the process is
• but just because it is complex, it doesn’t mean that there are certain crucial genes in the
functioning of the entire circuit
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o eg. Faithfulness related to a single gene
o it is a vasopressin receptor gene, when expressed in different amounts can effect
levels of faithfullness
o there was a switch that would change polygamous animals into monogamous
animals
▪ it isn’t the gene that causes the faithful rather it is a switch that causes the
circuitry to respond in making the animal faithful
o did an experiment with two groups of wolves where one group was polygamous
and the other was monogamous
o the two groups were very similar, but scientists found that high vasopressin
receptor led to monogamy and low led to polygamy
o you can put the vasopressin gene into transgenic mice and see that high
expression of the gene, can lead to faithful mice
o when mice are generally polygamous in nature
• How can such a complex system can get modified by random mutation/natural selection
leading to increased fitness?
o If the mutation make it easy for the animal to reproduce then it is good
• How can such a complex system get modified in a way that leads to adaptation to local
conditions?
• What is the basis of natural selection? (selecting by phenotype, but allele frequency will
change only if there is genetic component)
• How can behaviour of the organism be modified in an adaptive way against this
complexity?
• How can one study such complex systems (mechanisms)?
• How can one ever connect the pillars of the gene to behaviour bridge?
• One gene one behaviour issue.
o A lot of people think that there is a single gene for each behavior
o But due to the complexity, it is not that simple
• The switch and the circuitry
o Some genes act as switches that allow behaviors to occur
o In that sense certain genes can influence behaviours but it acts in unison with the
rest of the circuitry for this to occur
• Genetic variance versus effects of genes.
o Genetic variance allows evolutionary change
o And it is not there not because evolutionary likes genetic variance, someone
caused this to happen
o Rather it just occurred to allow you to reproduce and pass down adaptive genes to
your offspring
o Natural selection is ambi- directional but in the long run it does favour
adaptability
Neurobiology
• The discipline that studies everything that is in between genes and behavior
• How the brain works
From simple reflexes to consciousness
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Document Summary
Biochemical pathways: shows how complex the process is, but just because it is complex, it doesn"t mean that there are certain crucial genes in the functioning of the entire circuit. Neurobiology: the discipline that studies everything that is in between genes and behavior, how the brain works. Simple behaviour, 1: the human knee-jerk reflex is a 2 neuron reflex pathway. Its so simple and fast that it doesn"t require any conscious effort. Most behaviours are more complex and are supported by multiple neurons. Sensory neurons -> central processing (interneurons) -> motor neurons. The neuron is a complex 3d cell with numerous dendrites. In the cerebellum: requires fine motor coordination, sends and receive a lot of signals and requires a lot of synaptic connections that allows a lot of neurons to connect to it. In reality the brain is packed, and there is no space between these neurons.
