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Started reading
September 25, 2024
Oh, that’s right, we’re a kind of animal. And it will be a challenge to figure out when we’re just like other animals and when we are utterly different.
House two female rats together, and over the course of weeks they will synchronize their reproductive cycles so that they wind up ovulating within a few hours of each other.
Mislila sam da je to odbacena ideja. Da kao samo to uocavamo kada nam se ciklusi preklope, sto je jednom u par ciklusa...
we use the same muscles as does a male chimp attacking a sexual competitor, but we use them to harm someone because of their ideology.
Hahhahhahahahahhaah
“Well, to make it more beautiful.”
That's crazy...
oxymoronic,
The biologies of strong love and strong hate are similar in many ways, as we’ll see.
extraterrestrial;
Automatic aspects of behavior (simplistically, the purview of layer 1), emotion (layer 2), and thought (layer 3) are not separable.
In a rodent, olfactory inputs are what the limbic system most depends on for emotional news of the world. In contrast, the primate limbic system is more informed by visual inputs.
Limbic function is now recognized as central to the emotions that fuel our best and worst behaviors,
The hypothalamus, a limbic structure, is the interface between layers 1 and 2, between core regulatory and emotional parts of the brain.
And thus the midbrain and brain-stem regions, along with their projections down the spine and out to the body, are collectively termed the “autonomic nervous system.”fn1
And where does the hypothalamus come in? It’s the means by which the limbic system influences autonomic function, how layer 2 talks to layer 1.
The autonomic nervous system has two parts—the sympathetic and parasympathetic nervous systems, with fairly opposite functions.
projections down the spine and on to outposts throughout the body, where the axon terminals release the neurotransmitter norepinephrine.
There’s one exception that makes the SNS more familiar. In the adrenal gland, instead of nor-epinephrine (aka noradrenaline) being released, it’s epinephrine (aka the famous adrenaline).fn3
Given that the SNS and PNS do opposite things, the PNS is obviously going to be releasing a different neurotransmitter from its axon terminals—acetylcholine.fn5
The cortex is the gleaming, logical, analytical crown jewel of layer 3. Most sensory information flows there to be decoded. It’s where muscles are commanded to move, where language is comprehended and produced, where memories are stored, where spatial and mathematical skills reside, where executive decisions are made.
First, the cortex is not a smooth surface but instead is folded into convolutions. The convolutions form a superstructure of four separate lobes: the temporal, parietal, occipital, and frontal, each with different functions.
The greatest lateralization occurs in the cortex; the left hemisphere is analytical, the right more involved in intuition and creativity.
In fact the functional differences between the hemispheres are generally subtle, and I’m mostly ignoring lateralization.
THE AMYGDALAfn8 IS the archetypal limbic structure, sitting under the cortex in the temporal lobe.
Sticking an electrode in someone’s amygdala and stimulating it (as is done before certain types of neurosurgery) produces rage.
In PTSD sufferers the amygdala is overreactive to mildly fearful stimuli and is slow in calming down after being activated.
the basolateral amygdala (BLA),
In other words, these neurons respond to the meaning of the stimulus, rather than to its specific modality.
When we stop fearing something, it isn’t because some amygdaloid neurons have lost their excitability. We don’t passively forget that something is scary. We actively learn that it isn’t anymore.fn19
In other words, the default state is to trust, and what the amygdala does is learn vigilance and distrust.
Studies like these clarify that the amygdala isn’t about the pleasure of experiencing pleasure. It’s about the uncertain, unsettled yearning for a potential pleasure, the anxiety and fear and anger that the reward may be smaller than anticipated, or may not even happen. It’s about how many of our pleasures and our pursuits of them contain a corrosive vein of disease.fn22,24
For starters, the amygdala, specifically the BLA, gets projections from all the sensory systems.
Thus the amygdala can be informed about something scary before the cortex has a clue.
This shortcut’s power is shown in the case of a man with stroke damage to his visual cortex, producing “cortical blindness.” While unable to process most visual information, he still recognized emotional facial expressions via the shortcut.fn23
the insular cortex processes gustatory disgust.
Remarkably, humans also activate it by thinking about something morally disgusting—social norm violations or individuals who are typically stigmatized in society.
As reviewed, typically the amygdala learns fear and the hippocampus learns detached, dispassionate facts. But at times of extreme fear, the amygdala pulls the hippocampus into a type of fear learning.
Ultimately, amygdala outputs are mostly about setting off alarms throughout the brain and body.
Axonal projections from there go to an amygdala-ish structure nearby called the bed nucleus of the stria terminalis (BNST). The BNST, in turn, projects to parts of the hypothalamus that initiate the hormonal stress response (see chapter 4), as well as to midbrain and brain-stem sites that activate the sympathetic nervous system and inhibit the parasympathetic nervous system.
The amygdala also activates a brain-stem structure called the locus coeruleus, akin to the brain’s own sympathetic nervous system.32 It sends norepinephrine-releasing projections throughout the brain, particularly the cortex.
the opposite of love is not hate, it’s indifference.
The dissociation between fear and aggression is evident in violent psychopaths, who are the antithesis of fearful—both physiologically and subjectively they are less reactive to pain; their amygdalae are relatively unresponsive to typical fear-evoking stimuli and are smaller than normal.34 This fits with the picture of psychopathic violence; it is not done in aroused reaction to provocation. Instead, it is purely instrumental, using others as a means to an end with emotionless, remorseless, reptilian indifference.
What does the frontal cortex do? Its list of expertise includes working memory, executive function (organizing knowledge strategically, and then initiating an action based on an executive decision), gratification postponement, long-term planning, regulation of emotions, and reining in impulsivity.
the frontal cortex makes you do the harder thing when it’s the right thing to do.
The human frontal cortex is more complexly wired than in other apes and, by some definitions as to its boundaries, proportionately bigger as well.
The sole exception is an obscure type of neuron with a distinctive shape and pattern of wiring, called von Economo neurons (aka spindle neurons). At first they seemed to be unique to humans, but we’ve now found them in other primates, whales, dolphins, and elephants.fn26 That’s an all-star team of socially complex species.
prefrontal cortex (PFC),
it’s the PFC that is “the decider.”
Once it has decided, the PFC sends orders via projections to the rest of the frontal cortex, sitting just behind it. Those neurons then talk to the “premotor cortex,” sitting just behind it, which then passes it to the “motor cortex,” which talks to your muscles. And a behavior ensues.fn27
cognition (defined by Princeton’s Jonathan Cohen as “the ability to orchestrate thought and action in accordance with internal goals”)?
In a great study, monkeys were trained to look at a screen of dots of various colors moving in particular directions; depending on a signal, a monkey had to pay attention to either color or movement. Each signal indicating a shift in tasks triggered a burst of PFC activity and, coupled with that, suppression of the stream of information (color or movement) that was now irrelevant. This is the PFC getting you to do the harder thing; remembering that the rule has changed, don’t do the previous habitual response.
The PFC is essential for categorical thinking, for organizing and thinking about bits of information with different labels.
