eli5: Why do most people have no memories from before age 4 or 5 years old?
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After reading some comments and stuff my main surprise from my own imagination is that I’m sure maybe it’s akin to nobody being able to cope with the trauma of birth if we were able to remember something like that. Everything is new to us and our mind is pretty much blown every single day. When was the last time any of us just simply had the thought “wow it’s so beautiful today”? We’ve basically rationalized every aspect of life at this point wether it’s subconsciously or not but I mean those younger years we don’t have knowledge and understanding while we explore everything around us. Idk just my thought
i took a class on memory about a year ago as an undergrad neurosci major. my professor did research on this specific question. her explanation was that there is a sensitive period during which we develop our ability to make long term memories. before we develop the ability to form longterm memories, we are said to be in a state of infantile amnesia.
a sensitive period is a period of time during which the environment greatly influences our development for certain characteristics such as language or the development of ocular dominance columns in primary visual cortex (this is the classic example in neuroscience, pretty much if you deprive one eye of sensory input during the sensitive period, you develop a lazy eye) in an irreversible way. in rodents (at least rats and mice) the sensitive period for forming longterm memories is from day 17-20 from birth, meaning that rodents before this period can’t remember things a day after learning them. im not sure if we know exactly when this sensitive period is in humans.
my professor’s lab did a series of experiments that showed a few interesting things about this phenomenon
1) learning a task during this sensitive period led to long lasting expression of proteins required for synapse formation and maturation. during the sensitive period, learning causes expression of these proteins that is long lasting and gradually ramps up over hours, as opposed to learning in adult rodents, where the expression of the same proteins peaks roughly 30 minutes after the learning session. the implication here being that much larger scale structural changes are occurring in the young brain during the sensitive period after a learning event than in the adult brain. there are also some differences in which specific proteins being expressed.
2) rodents require two training sessions. one at day 17 during the sensitive period, which develops their ability to form long term memories for a particular type of task, after which a second training session at day 19 will cause them to actually form a longterm memory. if you only provide one training session to a rodent at day 19, they won’t remember the task later on.
3) developing the ability to form long term memories during the sensitive period is task-dependent. training a rodent on one task during the sensitive period develops their ability to form long term memories for similar tasks but not tasks that are very different from the original task.
there’s a number of limitations here, such as there being so many different types of memory and so many different tasks. it’s unclear if this generalizes to all types of memory. the specific types of memory tested here are contextual fear conditioning and novel object location. its also unclear just how integral this sensitive period is for the general ability of rodents to learn later on as much older adults (rats that don’t undergo the specific task training during the sensitive period are presumably able to learn the task as full adults?). and there is also the big caveat that rodents are much different from humans. despite the limitations however, the hippocampal memory system is a super interesting topic and there’s a lot of work being done right now dissecting the specific mechanisms for how it develops.
link for the paper
https://www.nature.com/articles/s41467-020-14461-3#Sec2
i took a class on memory about a year ago as an undergrad neurosci major. my professor did research on this specific question. her explanation was that there is a sensitive period during which we develop our ability to make long term memories. before we develop the ability to form longterm memories, we are said to be in a state of infantile amnesia.
a sensitive period is a period of time during which the environment greatly influences our development for certain characteristics such as language or the development of ocular dominance columns in primary visual cortex (this is the classic example in neuroscience, pretty much if you deprive one eye of sensory input during the sensitive period, you develop a lazy eye) in an irreversible way. in rodents (at least rats and mice) the sensitive period for forming longterm memories is from day 17-20 from birth, meaning that rodents before this period can’t remember things a day after learning them. im not sure if we know exactly when this sensitive period is in humans.
my professor’s lab did a series of experiments that showed a few interesting things about this phenomenon
1) learning a task during this sensitive period led to long lasting expression of proteins required for synapse formation and maturation. during the sensitive period, learning causes expression of these proteins that is long lasting and gradually ramps up over hours, as opposed to learning in adult rodents, where the expression of the same proteins peaks roughly 30 minutes after the learning session. the implication here being that much larger scale structural changes are occurring in the young brain during the sensitive period after a learning event than in the adult brain. there are also some differences in which specific proteins being expressed.
2) rodents require two training sessions. one at day 17 during the sensitive period, which develops their ability to form long term memories for a particular type of task, after which a second training session at day 19 will cause them to actually form a longterm memory. if you only provide one training session to a rodent at day 19, they won’t remember the task later on.
3) developing the ability to form long term memories during the sensitive period is task-dependent. training a rodent on one task during the sensitive period develops their ability to form long term memories for similar tasks but not tasks that are very different from the original task.
there’s a number of limitations here, such as there being so many different types of memory and so many different tasks. it’s unclear if this generalizes to all types of memory. the specific types of memory tested here are contextual fear conditioning and novel object location. its also unclear just how integral this sensitive period is for the general ability of rodents to learn later on as much older adults (rats that don’t undergo the specific task training during the sensitive period are presumably able to learn the task as full adults?). and there is also the big caveat that rodents are much different from humans. despite the limitations however, the hippocampal memory system is a super interesting topic and there’s a lot of work being done right now dissecting the specific mechanisms for how it develops.
link for the paper
https://www.nature.com/articles/s41467-020-14461-3#Sec2
i took a class on memory about a year ago as an undergrad neurosci major. my professor did research on this specific question. her explanation was that there is a sensitive period during which we develop our ability to make long term memories. before we develop the ability to form longterm memories, we are said to be in a state of infantile amnesia.
a sensitive period is a period of time during which the environment greatly influences our development for certain characteristics such as language or the development of ocular dominance columns in primary visual cortex (this is the classic example in neuroscience, pretty much if you deprive one eye of sensory input during the sensitive period, you develop a lazy eye) in an irreversible way. in rodents (at least rats and mice) the sensitive period for forming longterm memories is from day 17-20 from birth, meaning that rodents before this period can’t remember things a day after learning them. im not sure if we know exactly when this sensitive period is in humans.
my professor’s lab did a series of experiments that showed a few interesting things about this phenomenon
1) learning a task during this sensitive period led to long lasting expression of proteins required for synapse formation and maturation. during the sensitive period, learning causes expression of these proteins that is long lasting and gradually ramps up over hours, as opposed to learning in adult rodents, where the expression of the same proteins peaks roughly 30 minutes after the learning session. the implication here being that much larger scale structural changes are occurring in the young brain during the sensitive period after a learning event than in the adult brain. there are also some differences in which specific proteins being expressed.
2) rodents require two training sessions. one at day 17 during the sensitive period, which develops their ability to form long term memories for a particular type of task, after which a second training session at day 19 will cause them to actually form a longterm memory. if you only provide one training session to a rodent at day 19, they won’t remember the task later on.
3) developing the ability to form long term memories during the sensitive period is task-dependent. training a rodent on one task during the sensitive period develops their ability to form long term memories for similar tasks but not tasks that are very different from the original task.
there’s a number of limitations here, such as there being so many different types of memory and so many different tasks. it’s unclear if this generalizes to all types of memory. the specific types of memory tested here are contextual fear conditioning and novel object location. its also unclear just how integral this sensitive period is for the general ability of rodents to learn later on as much older adults (rats that don’t undergo the specific task training during the sensitive period are presumably able to learn the task as full adults?). and there is also the big caveat that rodents are much different from humans. despite the limitations however, the hippocampal memory system is a super interesting topic and there’s a lot of work being done right now dissecting the specific mechanisms for how it develops.
link for the paper
https://www.nature.com/articles/s41467-020-14461-3#Sec2
I’ve often wondered this, as most of my friends don’t remember things before 5-6 years of age. My older sister and I both remember a lot of things from our youth, in vivid detail, and never really undersood why others didn’t.
For example, I remember crawling to my grandfather in the house my grandparents lived in. I remember the chair he sat in and him picking me up. I was 15 months old when he passed away. I’ve described the setting to my mother who couldn’t believe it. I also remember where my bedroom was, where the closet was and where my crib was and the mobile that hung above the crib, which again has been verified by my parents. We moved out when I was less than 2 years old.
I’ve only come across a few others that remember things before the age of 3, so I’d love some insight about why some people remember things so vividly while others don’t.
In neuroscience, there appears to be in inverse relationship between speed of learning and depth of retention. If a neural network is more flexible it can learn faster, but isn’t stable enough to reliably retain memories. This has been shown both in animal experiments, and in computer models of complex neural networks.
So there’s this tradeoff that your brain has to make. When you’re young, it trades memory-retention for fast learning because memories are less important at that stage than getting up to speed. As you age, memories become increasingly important. You learn slower relatively to a bb, but you retain more explicit memories.
When you’re extremely young your brain is making that tradeoff to its maximum extent.
Also, your memories are stored distributed over your entire brain, accessing them requires activating these subset-networks of neurons, each of which correspond to a memory. Babies don’t have any coherent networks to access, which further prevents memory formation. They don’t have the necessary apparatus to store the memories.
In neuroscience, there appears to be in inverse relationship between speed of learning and depth of retention. If a neural network is more flexible it can learn faster, but isn’t stable enough to reliably retain memories. This has been shown both in animal experiments, and in computer models of complex neural networks.
So there’s this tradeoff that your brain has to make. When you’re young, it trades memory-retention for fast learning because memories are less important at that stage than getting up to speed. As you age, memories become increasingly important. You learn slower relatively to a bb, but you retain more explicit memories.
When you’re extremely young your brain is making that tradeoff to its maximum extent.
Also, your memories are stored distributed over your entire brain, accessing them requires activating these subset-networks of neurons, each of which correspond to a memory. Babies don’t have any coherent networks to access, which further prevents memory formation. They don’t have the necessary apparatus to store the memories.
I’ve often wondered this, as most of my friends don’t remember things before 5-6 years of age. My older sister and I both remember a lot of things from our youth, in vivid detail, and never really undersood why others didn’t.
For example, I remember crawling to my grandfather in the house my grandparents lived in. I remember the chair he sat in and him picking me up. I was 15 months old when he passed away. I’ve described the setting to my mother who couldn’t believe it. I also remember where my bedroom was, where the closet was and where my crib was and the mobile that hung above the crib, which again has been verified by my parents. We moved out when I was less than 2 years old.
I’ve only come across a few others that remember things before the age of 3, so I’d love some insight about why some people remember things so vividly while others don’t.
There’s something here with trauma (at least anecdotally) at an early age that grants access to earlier memories. My very first memory of being alive is allegedly from when I was 2. At 5-5.5 years old I started getting pretty badly abused by my birth mother and step father. I spoke about a memory I have of my grandpa. He and my Grandma said it’s impossible I was only 2 when that happened. But none the less I have the memories.
There have been studies that show memories are held in our flesh, can and do get passed on to off spring. I think it was a study on epigenetics. In the study mice feet were shocked after a spray of citronella. Their kids after being born we’re exposed to the same stimuli and started freaking out from just the smell no shock. They say that’s why everyone is scared of the dark at some point in life, because huge animals used to eat us at night. ¯|_(ツ)_/¯
So I think we have the access to the memories but on a sub conscious level. Think about it as an operating system (early childhood memories) vs an app (adult memories). While we do see the OS it mainly does stuff behind the scenes while your browser is what you’re actively interacting with?
There’s something here with trauma (at least anecdotally) at an early age that grants access to earlier memories. My very first memory of being alive is allegedly from when I was 2. At 5-5.5 years old I started getting pretty badly abused by my birth mother and step father. I spoke about a memory I have of my grandpa. He and my Grandma said it’s impossible I was only 2 when that happened. But none the less I have the memories.
There have been studies that show memories are held in our flesh, can and do get passed on to off spring. I think it was a study on epigenetics. In the study mice feet were shocked after a spray of citronella. Their kids after being born we’re exposed to the same stimuli and started freaking out from just the smell no shock. They say that’s why everyone is scared of the dark at some point in life, because huge animals used to eat us at night. ¯|_(ツ)_/¯
So I think we have the access to the memories but on a sub conscious level. Think about it as an operating system (early childhood memories) vs an app (adult memories). While we do see the OS it mainly does stuff behind the scenes while your browser is what you’re actively interacting with?
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