I call heaven and earth to witness against you today, that I have set before you life and death, blessing and curse. Therefore choose life, that you and your offspring may live (Deut 30:19 ESV)
God in His Word gives us a choice - life or death. He then instructs us to choose life! We must make the effort to choose life with our every thought.
Satan can only directly influence our flesh
Our brain is part of our body, our flesh. If we are in Christ it appears the devil cannot directly touch our soul or our spirit which are both eternal (1 John 5:18). There do not appear to be any scriptures that indicate that Satan or his fallen angels or demons have any access to or have any direct influence over our soul or our spirit other than through our thoughts via deceptions, accusations or temptations (2 Cor 10:5, Rev 12:9, Zec 3:1, Rev 12:10, 1 Thes 3:5, Matt 4:1-3). This is done through our physical flesh, which he does have access to (1 Cor 5:5), by introducing the thought directly to our brain and then our mind is immediately made aware of the new "toxic" thought or an implanted or existing "toxic" memory. God himself gave us a spirit of love, power and a sound-mind/self-control (2 Tim 1:7), therefore His intention is that our spirit via God's Holy Spirit should have a positive influence over our soul (mind, emotions, will) and our minds should have control over our brains which in turn have control over our body.
"God does not bypass your mind [part of your eternal immortal soul] - He renews your mind. The devil will bypass it [your mind] - put a thought directly in your brain. God does not bypass it."Dr. Neil T Anderson, "Overcoming Depression," YouTube, https://www.youtube.com/watch?feature=player_embedded&v=YmBnyRijryU#t=2435
Our eternal immortal minds are very closely linked to our physical mortal brains. The devil can plant a thought in our brain which our mind discerns and then forwards with the emotional context of the thought to the will in order to make a decision to agree or disagree with that thought. Another example of the devil or his fallen angels planting a toxic thought directly in our brain is through dreams and nightmares. In some cases they seem so real that we will believe them as truth when in fact they are a lie. Certainly a nightmare cannot originate from God, who is love, because the fruit of the Spirit is love, joy and peace... A nightmare brings fear, terror, despair, anxiety, sadness, helplessness, hopelessness...
Based on current science it appears that the brain has physical counter parts to all three of the distinct parts of our soul - the mind, the emotions and the will.
The mind controls the conscious brain by controlling and directing our conscious thinking, meditation and decision making.
The emotions, which are felt not thought, are stored in the unconscious brain and processed in the brain by the hypothalamus, the amygdala, the hippocampus and the thalamus.
The will's physical counterparts, which carry out decision making, are the basal forebrain and the orbitofrontal cortex which are located behind the inside corners of your eyes and above your eyebrows respectively. 
Think of the brain as a computer - a piece of physical hardware. The computer can only do useful work if there is software to run it. Think of the mind as the software that makes the computer (our higher level conscious brain) function. The brain like the computer only stores and processes the data, our memories and new thoughts, according to our mind's oversight. We process all sorts of things internally and from external sources through our five senses. The devil can plant thoughts in our brain which our mind will automatically take notice of and then we make a decision to accept it or reject it by exercising our will - we choose. Many Christians and most non-Christians often think that a temptation or accusation (usually lies) comes only from within themselves when in fact the devil is the deceiver, the accuser and the tempter and many thoughts we have come from his kingdom.
1 Corinthians 5:5 (ESV)
you are to deliver this man to Satan for the destruction of the flesh [body], so that his spirit may be saved in the day of the Lord. [this appears to imply that even though the devil may have permission to bring harm to our body he and his angels and demons cannot touch our spirit]
Matthew 10:28 (ESV)
And do not fear those who kill the body [including the brain] but cannot kill the soul [mind, emotions, will]. Rather fear him who can destroy both soul and body [new immortal one] in hell.
Daniel 2:28 (ESV)
…there is a God in heaven who reveals mysteries, and he has made known to King Nebuchadnezzar what will be in the latter days. Your dream and the visions of your head as you lay in bed are these:.. [a scripture referring to the brain]
Ezekiel 3:7 (ESV)
But the house of Israel will not be willing to listen to you, for they are not willing to listen to me: because all the house of Israel have a hard forehead [physical] and a stubborn heart [spiritual]. [forehead: probably referring to a specific part of the brain]
In our brains the "frontal lobe" is the part of the brain just behind our forehead. Among other things, this area has been scientifically proven to be associated with choosing between good and bad actions. The "hard forehead" in Ezekiel 3:7 most likely refers to the mind/brain-emotions-will continually making choices contrary to the will of God. Constantly making the same bad decisions over and over again turns it into a "bad habit"/"toxic memory" because the habit is really just a very solid ("hard") long term memory stored in our brains. Memories are actually stored in physical proteins manufactured within our brains. Here is an example of a good "hard forehead":
Ezekiel 3:8-9 (ESV)
8 Behold, I have made your face as hard as their faces, and your forehead as hard as their foreheads. 9 Like emery harder than flint have I made your forehead. Fear them not, nor be dismayed at their looks, for they are a rebellious house.
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Isaiah 26:3 (ESV)
You keep him in perfect peace whose mind is stayed on you, because he trusts in you.
Romans 8:6-7 (ESV)
For to set the mind [part of the soul] on the flesh [the body including the brain] is death, but to set the mind on the Spirit is life and peace. For the mind that is set on the flesh is hostile to God, for it does not submit to God’s law; indeed, it cannot.
Philippians 4:7 (ESV)
And the peace of God, which surpasses all understanding, will guard your hearts and your minds in Christ Jesus.
James 1:2 (ESV)
Count it all joy, my brothers, when you meet trials of various kinds. [No matter the situation, in Christ we should hold onto joy.]
Philippians 4:4 (ESV)
Rejoice in the Lord always; again I will say, rejoice.
The opposite of Joy:
anxiety, depression, melancholy, misery, sadness, seriousness, sorrow, unhappiness, discouragement, dislike, mourning, woe…
Every memory stored in our brain is stored along with an associated emotion. Which emotions do you want permanently stored?
What is the opposite of our will deciding to do something out of love? Choosing to do something out of selfish self-centeredness, self-serving, self-preservation, out of various fears for self. Fear of dying, fear of the devil, fear of people, fear of failure...
1 John 4:8
Anyone who does not love does not know God, because God is love.
1 John 5:3 (ESV)
For this is the love of God, that we keep his commandments...
John 14:24 (ESV)
Whoever does not love me does not keep my words. And the word that you hear is not mine but the Father's who sent me.
2 Timothy 1:7 (ESV)
for God gave us a spirit not of fear but of power and love and self-control.
1 Corinthians 13:4-6 (ESV)
4 love is patient and kind; love does not envy or boast; it is not arrogant 5 or rude. It does not insist on its own way; it is not irritable or resentful; 6 it does not rejoice at wrongdoing, but rejoices with the truth.
Science confirms that our brain has been "wired" by our Creator for love. We were created in the image of God who is love. The chemicals that our brain releases when, by our will, we choose to practice 1 Cor 13:4-6 have been proven to bring peace to our minds and joy to our hearts and health to our bodies. When we choose the opposite of love, such as choosing based on fear, our brain releases chemicals that stop healthy cell growth not only in our brain but also in the rest of our body. (See Dr Bruce Lipton - The Brain & Body's Response to Love & Fear)
Righteousness also is important in directing the will. In the following two verses love and righteousness appear to be interchangeable. We cannot love if we are not practicing righteousness and we cannot practice righteousness without love (Hosea 10:12, 1 John 3:10).
Romans 14:17 ESV
For the kingdom of God is not a matter of eating and drinking, but of righteousness, peace and joy in the Holy Spirit
Galatians 5:22-23 ESV
But the fruit of the Spirit is love, joy, peace...
Romans 8:6 ESV
For to set the mind on the flesh is death, but to set the mind on the Spirit is life and peace.
To "set the mind" is a choice of the will. If we choose to set our minds on the flesh we will be following the path of the red arrows in the diagram at the top of this page which leads to death. If we choose to set our minds on the Spirit we follow the path of the purple arrows in the same diagram which leads to life and peace (of mind).
...I have set before you life and death... (Deut 30:19 ESV)
Proverbs 23:7 (NKJV)
For as a man thinks in his heart, so is he. [We are what we think. Do we think that we are children of God and heirs and co-heirs with Christ and are we living our lives according to these truths?]
2 Corinthians 10:5 (ESV)
We destroy arguments and every lofty opinion raised against the knowledge of God, and take every thought captive to obey Christ [We need to actively make every effort to train ourselves to examine every thought that enters our consciousness and reject all thoughts that don't match up with The Word - Jesus Christ. A mature Christian is one who has, over time and with perseverance, trained himself or herself to do this.]
Romans 12:2 (ESV)
Do not be conformed to this world, but be transformed by the renewal of your mind, that by testing you may discern what is the will of God, what is good and acceptable and perfect. [We need to renew our minds by rejecting the philosophies of the world directed at our minds and replace them with God's truths - especially of who we are in Christ]
Matthew 6:30-34 (ESV)
30 But if God so clothes the grass of the field, which today is alive and tomorrow is thrown into the oven, will he not much more clothe you, O you of little faith? 31 Therefore do not be anxious [worry], saying, ‘What shall we eat?’ or ‘What shall we drink?’ or ‘What shall we wear?’ 32 For the Gentiles seek after all these things, and your heavenly Father knows that you need them all. 33 But seek first the kingdom of God and his righteousness, and all these things will be added to you.
34 “Therefore do not be anxious [worry] about tomorrow, for tomorrow will be anxious [worry] for itself. Sufficient for the day is its own trouble. [Anxiety and worry are things we think about. We need to replace the worry with faith that God will provide for our needs as He promises He will. The original Greek word is merimnaō and is "an old verb for worry and anxiety – literally, to be divided, distracted" - things the devil encourages us to be.]
1 John 4:1 (ESV)
Beloved, do not believe every spirit, but test the spirits to see whether they are from God [We need to reject thoughts that do not come from God]
Ephesians 6:16 (ESV)
In all circumstances take up the shield of faith, with which you can extinguish all the flaming darts of the evil one [We need to use the armor God has given us to reject the deceptions, accusations and temptations that the devil shoots at our mind/brain]
James 4:7 (ESV)
 [Humbly] submit yourselves therefore to God.  Resist the devil, and  he will flee from you.
I call heaven and earth to witness against you today, that I have set before you life and death, blessing and curse. Therefore choose life, that you and your offspring may live. [We need to choose life by an active decision of our God given will. Choosing life means choosing love, joy and peace over any other alternative.]
Philippians 4:8 (ESV)
Finally, brothers, whatever is true, whatever is honorable, whatever is just, whatever is pure, whatever is lovely, whatever is commendable, if there is any excellence, if there is anything worthy of praise, think about these things.