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The Right Memory at the Right Time A complex dialog across brain regions helps us retrieve useful and appropriate memories

Howard Eichenbaum has published a new study suggesting that the circuitry in the human brain that retrieves memories appropriate for specific situations spans long distances and supports a complex dialog between two brain structures. Photo by Cydney Scott

You’ve got a plan to pick up groceries for dinner on the way home. Right now, though, you’re in your office, coffee in hand. A co-worker drops by asking what materials are needed for an upcoming meeting.

Your answer, most likely, isn’t “carrots.” That’s because the human brain contains circuitry that retrieves memories appropriate for the current situation.

New work from the lab of Howard Eichenbaum, Boston University William Fairfield Warren Distinguished Professor and director of BU’s Center for Memory & Brain, suggests that this circuitry spans long distances in the brain and supports a complex dialog between two brain structures. The work, published online on June 20, 2023, in Nature Neuroscience, is among the first to describe the operations of a large brain circuit that controls complex behavior. By revealing the details of the communications between brain regions to access appropriate memories, the findings may give clinical researchers clues about which communication channels may be impaired in brain disorders that disrupt memory.

“Understanding this system has implications for almost any disorder that affects memory, from schizophrenia, depression, and epilepsy to traumatic brain injury and post-traumatic stress disorder,” says Charan Ranganath, a neuroscientist at the University of California, Davis, who studies human memory but was not involved in this research. “We’re really interested in understanding the ability to use knowledge to make decisions.”

Foraging for Froot Loops

To study a complex human behavior, such as remembering appropriate information at the right time, Eichenbaum had to train rats to memorize an important piece of information and then find a way for them to use it. So his team trained rats to find Froot Loops in flowerpots. “Rats are absolutely nuts about Froot Loops,” he says.

As the rats navigate from room to room, Eichenbaum’s team records their brain activity using electrodes inserted into the brain. They monitor both the hippocampus, known to be the seat of memory in the brain, and the prefrontal cortex, thought to be a coordinator.

In previous studies, the team had already learned that neurons in the prefrontal cortex fire in relation to cues that signal rewards, such as a particular pot that contains a stash of Froot Loops. They had also identified neurons in a region called the ventral hippocampus that recognize the room the rat is in. Neurons in the dorsal hippocampus fire when the rat recognizes a flowerpot it has seen before. In this most recent experiment, they learned how the brain puts these pieces of information together to guide a decision, like which pot to dig in.

Memory with Purpose

This handshaking is important because many things can go wrong to interrupt it. When Eichenbaum’s team temporarily disabled the prefrontal cortex, the rats foraged in every pot, not because they don’t recognize the pots but because they don’t know which pot contains a reward based on the room they are in. “The prefrontal cortex has a very specific role,” says Eichenbaum. “It doesn’t activate the right memories, but rather it prevents the wrong memories from intruding.”

This finding may be relevant to human diseases like schizophrenia. People with this disorder don’t have trouble remembering things but often have trouble filtering out irrelevant or inappropriate information. “If the hippocampus remembers something, it’s the sound of one hand clapping,” says Ranganath. “It doesn’t help you unless it reaches areas that can use the information to make a decision or action.”

There is no direct anatomical connection in the brain between the prefrontal cortex and dorsal hippocampus, so it isn’t clear how messages are passed between them. But Eichenbaum’s studies suggest that there may be an indirect, bidirectional route that involves slow, pulsing brain rhythms called theta rhythms. These rhythms originate in deep structures in the middle of the brain, synchronize between the hippocampus and the prefrontal cortex, and allow information to flow between them.

To explore this possibility, Eichenbaum is using optogenetics, a powerful tool that allows researchers to configure specific neurons in the brains of rats so that they can be turned on or off using laser light. “We hope to trace the whole pathway of the circuit that is crucial to this dialog,” says Eichenbaum.

Theta rhythms are an important clue for researchers like Ranganath, too. “We’ve got to study theta activity in the human brain now that we think it’s related to your ability to remember the things you need to remember when you need to remember them,” he says.

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How The Human Nose Helps Chemists Analyze Flavor

Think you know the fresh, lemony taste of lemongrass, or the lush herbal taste of basil? Most of what we experience as “taste” actually comes from our sense of smell, not from our tastebuds. Volatile compounds — molecules light enough to produce a vapor or gas — play a key role in how we experience food and drink (as well as fragrances and scents). But the complex ways in which we perceive these molecules as flavor is not nearly as straightforward as pure chemistry, making understanding flavor partly, but not completely, a chemical question.

Using a gas chromatograph-mass spectrometer (GC-MS), a laboratory instrument that separates and detects the concentrations of mixtures of volatile compounds, we can easily quantify the aroma molecules in, say, a cup of coffee. But we still can’t ascertain which of these molecules are most important to its overall flavor, be it nutty, chocolatey, or fruity.

As a result, chemists have had to develop new ways to study chemistry and aroma perception in tandem. Perception behaves in complex and unpredictable ways — ways that even the most high tech lab equipment cannot decipher. Let’s say you have equal amounts of vanillin, the main aroma compound in vanilla, which is also found in wood-aged Scotch; and rotundone, the main aroma compound in black pepper, which also gives shiraz wines their spicy aroma. It stands to reason that, in equal concentrations, the aromatic intensity of both compounds should be identical, but in fact the rotundone will be approximately 1,000 times more intense-smelling than the vanillin. Clearly, there is more to a flavor profile than just the concentration of its compounds.

While it’s true that the higher the concentration of a given compound, the more you’ll smell it, the intensity of an aroma compound at a given concentration is also heavily influenced by the chemical structure of the compound itself, which determines how it will interact with our olfactory receptors. The only way to properly analyze a smell is to smell it for yourself. Or, more accurately, to have a whole panel of people smell it for themselves, and then compare their perceptions.

One of the best ways to do so uses a technique called gas chromatography-olfactometry, or GC-O, which uses chemical separation (or chromatography) in conjunction with a human “sniffer.” Invented around 1950 to analyze, among other things, the volatiles responsible for aroma, gas chromatography enables analytical chemists to explore how the odor of different samples change as they are broken into their component chemical compounds. In a 1964 paper called “Volatile Esters of Bartlett Pear,” seminal analytical chemist Walt Jennings noted that some of the less volatile, “high-boiling” compounds from pears smelled reminiscent of pear jam, hypothesizing that part of the smell of cooked pears was actually present in their fresh counterparts, all along, but was masked by more volatile compounds until these evaporated during the cooking process.

Bartlett Pears

At around the same time, chemists at Colgate-Palmolive began collaborating with professional perfumers, using them as “human sensors” to describe the aromas of compounds isolated using gas chromatography. Drawing on the highly attuned palates of these aroma experts, they were able to pinpoint exactly which compound (in this case, anisaldehyde, a floral-smelling molecule) was responsible for the difference in aroma between two similar samples of pine oil. Without separation by gas chromatography, the perfumers could only smell the whole mixture, and without the perfumers, the chemists couldn’t identify which chemical differences actually impacted smell. The technique proved so useful, and was so easy to use, that over the past 50-plus years it has been used on everything from whiskeys and wines to perfumes to meats and plants.

Why analyze flavors? A palate finely tuned by lots of smelling and tasting gives us a strong basis for understanding flavor, but understanding the underlying chemistry opens up a brand-new toolbox for practitioners of flavor, be they food chemists, chefs, or perfumers. By understanding which molecules are responsible for the aromas we like, we can take better-informed steps to encourage or preserve them. In the food industry, GC-O is used to guide processing to do exactly this, and to enable entirely new scents and flavors. In research, once we’ve pinpointed the compounds responsible for flavor, we can make connections from climate and biochemistry all the way up to eating that help explain what make products with terroir or varietal character — like wines — so special. We can use flavor chemistry to invent new flavor combinations, opening up possibilities via a deeper understanding of how our actions in the kitchen affect flavor on a molecular level.

GC-O is not yet able to connect every dot between how we perceive an aroma and the chemistry behind it. Mixing aromas yields unpredictable results, with some compounds enhancing the intensity of others (beta-damascenone, a fruity, balsamic-smelling compound found in apples, roses, tobacco, and wine, for instance, is known to do this) and others (like 2,4,6-tricholoranisole, which is responsible for “corked” wine) masking the smell of the compounds they are mixed with. Complicating matters further, taste and the other senses can have a small but significant effect on how aromas are perceived. GC-O can’t tell us everything about an aroma, but it is an essential tool for figuring out how constituent compounds, each at unique concentrations, work together to create the kaleidescope of flavors we perceive every day.

Arielle Johnson loves food and flavor so much she decided to do a PhD on the subject. She is a doctoral candidate at UC Davis. Exactly how complex mixtures of molecules like wine and food get translated into flavor is not well understood by science, and her work focuses on this “black box,” especially in the context of eating and gastronomy. She hopes her work will help illuminate new knowledge and provide tools to chefs in the kitchen. Currently working on a sensory analysis of new Danish vinegars at the Nordic Food Lab houseboat in Copenhagen, an offshoot of Noma, she is also a contributor to the book The Kitchen as Laboratory.__

Learn How Does The Numpy.clip() Function Works?

Introduction to Numpy.clip() in Python

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In simpler terms for an interval specified (for instance : [0, 1]) the values that are greater than 1 shall deem to become one and the ones smaller than zero shall deem to become zero. In comparison to using the function min() and max() and checking their comparatives by maximum(), the clip() serves a much quicker and more comprehensive solution when compared to running the while loop.

Syntax and Parameters for Numpy clip()

Following syntax is used structurally to construct code in python language:

numpy.clip (arr, a _min, a_max , out = None)

Following are the parameters that are used in the syntax for numpy.clip() function in Python:

Parameters Description

array ( here arr) (alternatively, can be specified within the code itself)

(Scalar value, keyword: “arraylike” or keyword: “None”) If NONE is specified then the lowest element of the array would be considered to be the smallest element in the array entered. It has to be noted that the parameter NONE should not be specified for both a_min and a_max.  If either one of the parameters is kept as ARRAYLIKE it results in 3 different arrays being broadcast.

(Scalar value, keyword: “arraylike” or keyword: “None”) The highest value to be put for the array limit is the upper extent with which the array elements have been checked if they are larger than the lower limit.

Return Value when running through Numpy.clip()

This Numpy.clip() function returns a two-dimensional array that has been specialized from the string of elements that have been presented in the array.

numpy.clip ( arr,a_ min, a _ max, out  = None )

Returns: Here the lower values are replaced by a_min values and higher limits are replaced by a_max

Example of Numpy.clip()


# To demonstrate the usage of the Numpy clip () function in python language # calling the Numpy by importing it to perform the clip function import numpy as N1 Ar_array = [10 , 20 , 30 , 40 , 50 , 60 , 70 , 80 ] print ("Please enter the elements for the array :- ", Ar_array ) Output_array = N1.clip(Ar_array, a_min = 20 , a_max = 60 ) print ("The new clipped array will be : " ) print Output_array

The output of the above-given code is as follows:

How does the Numpy.clip() function work?

It is found in a lot of data concerning issues and algorithmic functionalities (for instance the Proximal Policy Optimization or PPO used in algorithms of reinforcement learning) where there is a need to limit the elements under an upper or lower value or both.

The numpy clip serves the purpose of delivering a pre-built functionality of limiting the values.

The following diagram pictographically displays how the clip function actually works and gives an insight into its mechanism of limiting

Fig: The image here displays how the default values using index numbers are identified and put under the clipped limit values

The system first analyses the values present in the array entered by the user

It then checks the limits for both the upper value and lower value

It then compares with each element if it does not confer to the limits and checks for their index with respect to the initial array entered

It changes the defaulting dex number to the upper limits and lowers limits specified.

Finally, it changes the values with the replaced limited values and makes a new array that suffices the need specified for the function to be performed by the user


The numpy clip function serves as one argument/liner solution to give clipped arguments for arrays which are frequently required by various algorithms which in a wat reduce the computational time needed to run code. It also decreases the verbosity of the code making it better for large data analysis.

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How Does Your School Plan For The Fall?

During the last week of school, our junior high carved out time alongside field trips and awards ceremonies for teachers to meet and reflect on the routines of departments, teams, and daily routines in the school so that we can imagine how things can be better for the next school year. Ethical approaches to teaching are about the continuous questioning and study of “how” our conduct and systems can not only be more efficient (though that is part of it) but also live up to ethical standards of what is “right” and “moral” or what schools “ought” to do.

No doubt you’ve felt the stress of the year winding down and you are eager to start your summer break, but what a relief it has been for me (and I think a few other colleagues) to have some important conversations about our school and how we are relating to one another before we go our separate ways for the summer.

I attended four meetings this week (about two hours a piece), and it was clear to me that every teacher in those meetings had ideas about how schedules and systems can be improved. And it seemed clear that some desperately needed to be a part of a conversation that had some hope.

In the meetings, we talked about a variety of topics. We considered how we are using what is not quite “home room” time and suggested ways to make that more meaningful. We talked about the need and value of a master calendar for testing, field trips, and assemblies to recognize instances where instructional time is enriched or interrupted. We also had a pretty detailed conversation about how to start the next school year.

This school year, our “kickoff” assembly was at the end of the week, and we decided that next year we’d make that a “welcome” assembly within the first hour of the first day of school. Kickoff at the beginning. Seems logical, yes? Perhaps these conversations seem obvious, and yet, we have, in the past, waited until August to talk about the “hows” of our school. I see these meetings as evidence of ethics – not in the sense that having the assembly early in the week is necessarily more “right,” but in the sense that an ethical standard of being welcoming to our students informed our decision-making. It is a slight shift in thinking, but I think it is important.

Ethics refers to standards of right and wrong or what we “ought” to do in terms of virtues like obligations and human rights, but ethics also include virtues of compassion and community. In addition, ethics can refer to the development of ethical standards and the ongoing study of moral beliefs and conduct to make sure that the institutions we help shape – like our schools – are evaluating and adjusting approaches for the “right” reasons.

Of course, what is “right” can seem relative, and figuring out if there is a more just approach to a routine or system (especially among a group of teachers) is complicated; however, meetings like we had this week are an imperative as schools figure out the sort of learning environment they want to be, need to be for their students – the human beings with whom we are entrusted.

Teachers know there is no such thing as “summers off.” You are reading a blog about teaching now. It may be too late to talk about routines in home room or master calendars, but here are a few questions to consider before starting the next school year (after all, ethical ELA is more about questions than answers):

How Does The Filter_Var Function Work In Php?

Introduction to PHP filter_var

Php filter_var() is a function that is used to filter a given variable with a specified filter. To sanitize and validate the data such as email_id, IP address, etc., in Php, the filter_var() function is used (which contains the data). Validation in the text means whether the entered data is in the correct format or not. For example, in an email id of the person, whether the ‘@’ sign is present or not. In a phone number field, all the numbers or digits should be present. Sanitization means to sanitize the data entered or remove the illegal or unnecessary characters from it to prevent any future issues. For example, removing unnecessary symbols and characters from user email.

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filter_var(variable, filtername, options)


variable: This parameter stands for the variable field, the variable which needs to be filtered. It is the mandatory field.

filtername: This parameter stands for the name of the filter which the user wants to use. It is an optional parameter. If not specified, FILTER_DEFAULT is used, which means that not filtering would be done to the given variable.

options: This parameter is optional. It specifies the options/ flags to be used. It is basically an associative array of bitwise disjunctions of flags or options. If this parameter is used in the filter_var() function, a flag must be provided in the ‘flags’ field, and a callable type must be passed for the callback function. After accepting all the parameters, the filtered and sanitized variable is returned.

Return Value: The above function returns the filtered value or false if the data/ variable does not get filtered.

How does the filter_var function work in Php?

In PHP, the filter_var() method accepts the above-explained various parameters and returns the validated/ sanitized data. Validation means checking the format of the data as specified by the programmer, and Sanitization means removing the unnecessary characters from the data to return the data as required by the programmer.

Examples of PHP filter_var

Let us understand the working of the filter_var() function in Php along with the examples:

Example #1

Validating an Integer value using filter_var() function:


<?php $value = 789787; if (filter_var($value, FILTER_VALIDATE_INT)) { echo(“Congratulations!!! $value is a valid integer value”); } else { echo(“Sorry!! $value is not a valid integer value”); }



In the above code, the Integer value to be validated is stored in the variable ‘value’ and is then passed in the filter_var() method along with the ‘FILTER_VALIDATE_INT’ filter name to validate it. Finally, conditional operators if and else are applied to check the condition, and the respective output is printed on the console using the ‘echo.’

Example #2

Validating the IP address of the computer device using the filter_var() function


<?php $ip = ‘180.0.0’; if (filter_var($ip, FILTER_VALIDATE_IP)){ echo(“Congratulations!! $ip is a valid IP address, passed by the you”); } else { echo(“Sorry $ip is an incorrect IP address”); }


In the above code, the IP address of the computer or any other network device is validated using the filter_var() method. The ip address that is to be validated is stored in the variable ‘ip.’ Since the IP address has its specific format ‘x.y.z.w,’ it is validated using the ‘FILTER_VALIDATE_IP’ in the filter_var() function. Finally, the ip address passed is validated, and the respective output is printed on the console using ‘echo.’

Example #3

Sanitizing and Validating the URL address using the filter_var() function


<?php $check_url = filter_var($check_url, FILTER_SANITIZE_URL); if(!filter_var($check_url, FILTER_VALIDATE_URL) == false) { echo(“Congratulations!!! $check_url is the correct URL”); } else { echo(“Sorry!! $check_url is an invalid URL”); }



In the above code, the URL address, which has a specific format, is sanitized first and then validated using the filter_var() method. The URL to be checked is stored in the variable ‘check_url.’ To sanitize the url, ‘FILTER_SANITIZE_URL’ is passed as a filter name along with the url. Once sanitized, url is then validated using the ‘FILTER_VALIDATE_URL’ filter name along with the url, and the respective output on validation is printed on the console using ‘echo.’

Example #4

Validating the email address of the user using the filter_var() function


<?php $email_check = “[email protected]”; if (filter_var($email_check, FILTER_VALIDATE_EMAIL)) { echo(“Congratulations!! $email_check is a valid email address”); } else { echo(“Sorry!! You have entered an incorrect email address”); }


In the above example, the email address which is to be checked is stored in the variable ‘email_check.’ It is validated using the filter_var() function in Php, bypassing the email variable and the respective filter name (FILTER_VALIDATE_EMAIL). Since the passed email is invalid, so the response is printed on the console using the ‘echo.’

Example #5


<?php $value = 465675; { echo “Integer $value is within the specified range”; } else { echo “Sorry!! Integer $value is not in the range provided by you”; }



In the above example, the Integer value is to be validated for the given range, i.e., 10 to 400 is tested. Then, in the filter_var() function, the value to be tested is passed along with the filter name (FILTER_VALIDATE_INT) and 1 optional parameter, i.e., ‘options’ having the array with the minimum and maximum range specified. Finally, the variable is validated, and accordingly, the response is printed on the console using the ‘echo.’


The above description clearly explains what is filter_var() functions in Php and how it works to validate and sanitize the variable passed in it. It is one of the important functions that programmers commonly use to filter the data to prevent a security breach. However, this function facilitates the use of different filters by passing the different parameters according to the specific requirements, so the programmer needs to understand it deeply before using it in the program.

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Human Genome Project Goals Significance


The project began in 1990 and was completed in 2003, costing approximately $3.8 billion and involving hundreds of scientists worldwide.

Human genome project goals

The human genome project was completed in 2003 and had four main goals−

To read and decode one percent of the genome

To sequence at least 90% of the protein-coding genes in the human genome

To identify and map at least 10% of all human genes

To understand how the information encoded in DNA is converted into proteins.

Methods of the human genome project

The Human Genome Project is a global scientific endeavor aimed at understanding and mapping our minds. It was started in 1990, and the project is anticipated to be completed in 2005.

The Human Genome Project has three phases− 1) sequencing, 2) analysis and 3) technology development. The sequencing phase aims to assess all three billion base pairs in the human genome. The analysis stage involves the interpretation of data produced by the sequencing phase. The technology stage involves the development of bioinformatics and DNA chip technologies to aid in the analysis process.

The process of the human genome project

Scientists hope to uncover cures for many diseases and other ailments by studying genes and proteins. Although it took 13 years and $3 billion dollars to complete, the project has already discovered many important things about human genetics.


Identifying all human genes (sequencing) and determining their functions

Determining the order of bases in the DNA strand

Discovering the sequences in which genes are found on chromosomes.

The human genome is composed of twenty-three pairs of chromosomes. Each chromosome contains thousands of genes that are responsible for the production of proteins. Genes are essentially the blueprints for our bodies, and they determine everything from hair color to blood type to our risk for developing certain diseases.

The human genome project was one step closer to understanding how genetics work on a molecular level, which could potentially lead to new treatments/treatments for genetic diseases such as Alzheimer’s, Parkinson’s, diabetes, and cancer. It also helps us better understand how humans came into being in the first place and why they look and act (and get sick) the way they do.

Applications of HGP

The human genome project is a massive undertaking with numerous global benefits. Understanding the function of our DNA will allow researchers to develop new treatments for genetic diseases, create designer drugs that target specific ailments, and possibly even unlock the secrets of longevity. However, many people mistakenly believe that understanding DNA is the same as understanding life itself. In reality, it is only one small step on the long road to truly understanding life.


Most people agree that the results of the Human Genome Project have been a success. Researchers deciphered the entire human genome and made it available to be used for scientific, medical, and business purposes.

The project has helped researchers understand how genetic mutations lead to certain diseases and has made it easier for scientists to develop new ways of preventing those mutations from occurring in the first place. While many experts believed that the project would lead to new treatments, cures, and preventative measures within a few years, others argued that the effects would take much longer to become apparent−if they ever did at all.

Though there is still much more work to be done, it is clear that the Human Genome Project has provided invaluable information about our genetic makeup and presents healthcare professionals with potential opportunities to prevent or treat diseases such as cancer, heart disease, and diabetes. Thanks to this project, millions of people have benefited from its findings.


The Human Genome Project was a large, expensive undertaking with the goals of mapping and sequencing the human genome. The project was completed in 2003, and the results have been used in a variety of ways to improve human health. The project has also helped researchers to better understand the biology of a variety of diseases.


1. What is the Human Genome Project?

Ans: It was the goal of the Human Genome Project, a multinational endeavor to discover the sequence of chemical base pairs that make up human DNA. Work on the project started in 1990 and was completed in 2003.

2. What does “sequencing” mean?

Ans: Sequencing is the process of determining the order of nucleotides in a strand of DNA or RNA (ribonucleic acid). A single strand of DNA is made up of two chains, called polynucleotide chains, and each chain contains one strand of deoxyribose (DNA) or ribose (RNA).

Each nucleotide has three components− a phosphate group, a pentose sugar (either deoxyribose or ribose), and one of four bases− adenine (A), guanine (G), cytosine (C), or thymine (T). Phosphate and pentose sugars are always present in equal numbers. The four bases are present in different amounts. For example, one chain may have 20 A’s but only 10 C’s.

3. What are the benefits of knowing our DNA?

Ans: The Human Genome Project has yielded many benefits, including−

New ways to diagnose diseases such as cancer and Alzheimer’s disease

New treatments for diseases like cancer, heart disease, diabetes, and other illnesses

Better ways to predict people’s response to drugs like antibiotics and chemotherapy.

4. What are the benefits of sequencing an organism’s genome?

Ans: Sequencing an organism’s genome provides valuable insights into its genetic structure, function, and evolution, the knowledge that can be used to develop new treatments for disease and improve our understanding of biology in general. For example, human geneticists have already identified more than 1,000 disease-related genes based on their association with human diseases or traits such as height or earwax consistency/color.

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